Method and Apparatus for Obtaining Reference Signal

ABSTRACT

This application relates to the mobile communications field, and in particular, to a technology for obtaining a reference signal in a wireless communications system. In one example method for obtaining a reference signal, a terminal device obtains position offset information. The terminal device obtains a first sequence based on the position offset information. The terminal device demodulates, by using the first sequence, a control channel signal carried in a control channel resource set to obtain downlink control information.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.16/894,011, filed on Jun. 5, 2020, which is a continuation of U.S.patent application Ser. No. 16/355,157, filed on Mar. 15, 2019, now U.S.Pat. No. 10,693,694, which is continuation of International ApplicationNo. PCT/CN2018/095881, filed on Jul. 17, 2018, which claims priority toChinese Patent Application No. 201710687455.9, filed on Aug. 11, 2017.All of the aforementioned patent applications are hereby incorporated byreference in their entireties.

TECHNICAL FIELD

This application relates to the mobile communications field, and inparticular, to a technology for obtaining a reference signal in awireless communications system.

BACKGROUND

In a Long Term Evolution (LTE) network, a base station usually allocatesa part of system bandwidth regions to a specific terminal device. Thatis, within a specific time, resources in a specific frequency region areallocated to the terminal device. In this case, if the base stationpreferentially allocates high-quality resources in the specificfrequency region to the terminal device, so that service quality of theterminal device is better ensured, a reference signal may providereference for the base station during resource scheduling in thisprocess.

At a same time, reference points of a plurality of broadcast channelscoexist in frequency division multiplexing mode. For a method forgenerating first sequences corresponding to the reference points of thebroadcast channels, refer to a method for generating a user equipment(UE) specific reference signal in the LTE network. A resource of onecontrol channel resource set overlaps that of another control channelresource set on an orthogonal frequency division multiplexing (OFDM)symbol, and first sequences on reference signal resources included inresource element groups (REGs) on overlapping time-frequency resourcesare different.

Because a plurality of control channel resource sets overlap each otheron time-frequency resources, and initial values of different referencesignal sequences are different, sizes of overlapping resources do notaffect configuration modes of the reference signal sequences.Consequently, reference signal sequences mapped to the overlappingresources are different, orthogonal code division multiplexing of aplurality of reference signals on the overlapping resources cannot beimplemented, and multi-user multiple-input multiple-output (MU-MIMO)transmission performance is limited.

SUMMARY

Embodiments of the present invention provide a method and an apparatusfor obtaining a reference signal, and a system to improve MU-MIMOtransmission performance.

According to a first aspect, an embodiment of this application providesa method for obtaining a reference signal. The method includes:obtaining, by a terminal device, position offset information; obtaininga first sequence based on the position offset information; anddemodulating.

In a possible design, the method further includes: generating, by theterminal device, a reference signal sequence; and obtaining the firstsequence from the reference signal sequence based on the position offsetinformation, where the first sequence is a subset of the referencesignal sequence.

In a possible design, the method further includes: receiving, by theterminal device, a master information block (MIB) sent by a networkdevice, where the MIB includes indication information of a firstrelative position and indication information of a second relativeposition, the first relative position is a position of a reference pointof a broadcast channel carrying the MIB, relative to a frequency domainreference point, and the second relative position is a relative positionof the control channel resource set relative to the reference point ofthe broadcast channel; and determining the position offset informationaccording to the first relative position indicated by the indicationinformation of the first relative position and the second relativeposition indicated by the indication information of the second relativeposition.

According to this solution, when reference points of a plurality ofbroadcast channels are sent in different frequency domain positions,reference signals used by control channel resources configured forreference points of different broadcast channels are selected from asame sequence. In addition, even if a plurality of control channelresources overlap each other, a same sequences in an overlapping region,and further, resource reuse by a plurality of users, for example,orthogonal MU-MIMO, can be implemented in the overlapping resourceregion. In addition, the MIB includes the position offset information ofthe control channel resources. This is advantageous to forwardcompatibility, and can flexibly avoid interference from a signal sent bya neighboring cell on the control channel resources.

In a possible design, the method further includes: receiving, by theterminal device, a MIB sent by a network device, where the MIB includesindication information used to indicate a third relative position, andthe third relative position is a position of a reference point of abroadcast channel carrying the MIB, relative to a frequency domainreference point; and the obtaining, by a terminal device, positionoffset information includes: determining, by the terminal device, theposition offset information according to the third relative positionindicated by the indication information of the third relative positionand a fourth relative position, where the fourth relative position is arelative position of the control channel resource set relative to thereference point of the broadcast channel, and the fourth relativeposition is configured or preset.

According to this solution, when a plurality of broadcast channels aresent in different frequency domain positions, reference signals used bycontrol channel resources configured for reference points of differentbroadcast channels are selected from a same sequence. In addition, evenif a plurality of control channel resources overlap each other, samesequences are used in an overlapping region, and further, resource reuseby a plurality of users, for example, orthogonal MU-MIMO, can beimplemented in the overlapping resource region.

In a possible design, the method further includes: receiving, by theterminal device, a master information block MIB, where the MIB includesindication information used to indicate eighth relative positioninformation of the control channel resource set relative to a frequencydomain reference point; and the obtaining, by a terminal device,position offset information includes: determining, by the terminaldevice, the position offset information according to the eighth relativeposition indicated by the indication information of the eighth relativeposition.

When a plurality of broadcast channels may be sent in differentfrequency domain positions, if this solution is used, a same frequencydomain reference point may be referenced by the obtained first sequence.Therefore, a plurality of overlapping control channel resources canshare a same reference signal sequence, and further, resource reuse by aplurality of users, for example, orthogonal MU-MIMO, can be implemented.In addition, relative position information of a control channel relativeto a reference point of a broadcast channel and relative positioninformation of the reference point of the broadcast channel relative tothe frequency domain reference point can be jointly encoded forindicating. This improves coding efficiency and reduces indicationsignaling overheads.

In a possible design, the method further includes: receiving, by theterminal device, configuration information of a bandwidth, where thebandwidth is a part of a system bandwidth, the configuration informationincludes indication information of a fifth relative position, and thefifth relative position is a relative position of a bandwidth comprisingthe control channel resource set relative to a frequency domainreference point; and the obtaining, by a terminal device, positionoffset information includes: determining, by the terminal device, theposition offset information according to the fifth relative positionindicated by the indication information of the fifth relative position.

According to this solution, the configuration information of thebandwidth may be carried in remaining minimum system information (RMSI)other than a MIB. Therefore, indication signaling overheads of the MIBare reduced. In addition, the RMSI may carry more bit information, andfurther, an offset of a bandwidth in frequency domain may be moreflexible, that is, an offset granularity in frequency domain may besmaller. Therefore, the offset of the bandwidth is more flexible, andresource utilization can be improved.

In a possible design, the method further includes: receiving, by theterminal device, configuration information of a bandwidth, where thebandwidth is a part of a system bandwidth, the configuration informationincludes indication information of a sixth relative position andindication information of a seventh relative position, the sixthrelative position is a relative position of a bandwidth comprising thecontrol channel resource set relative to a reference point of abroadcast channel carrying a MIB, and the seventh relative position is aposition of the reference point of the broadcast channel carrying theMIB, relative to a frequency domain reference point; and the obtaining,by a terminal device, position offset information includes: determiningthe position offset information according to the sixth relative positionindicated by the indication information of the sixth relative positionand the seventh relative position indicated by the indicationinformation of the seventh relative position.

According to this solution, the configuration information of thebandwidth may be carried in RMSI other than a MIB. Therefore, indicationsignaling overheads of the MIB are reduced. In addition, systeminformation (the RMSI) may carry more bit information, and further, anoffset of a bandwidth in frequency domain may be more flexible, that is,an offset granularity in frequency domain may be smaller. Therefore, theoffset of the bandwidth is more flexible, and resource utilization canbe improved.

In a possible design, the obtaining, by a terminal device, positionoffset information includes: receiving, by the terminal device,configuration information of the control channel resource set, where theconfiguration information of the control channel resource set includesindication information used to indicate the position offset information,obtaining, by the terminal device, the position offset informationaccording to the indication information used to indicate the positionoffset information.

According to this solution, when configuring time-frequency resources ofthe control channel resource set, a network device obtains anoverlapping resource region on the time-frequency resources, anddetermines the position offset information according to the overlappingresource region, and when configuring the control channel resource set,configures position offset information of a first sequence used by acontrol channel reference signal, so that reference signal sequences ofa plurality of control channels are the same in the overlapping region.Therefore, orthogonal reuse by a plurality of users, that is, orthogonalMU-MIMO, is enabled. In addition, non-orthogonal interference betweensequences that is caused by a plurality of different sequences on a samereference signal resource can be reduced.

For example, the indication information used to indicate the positionoffset information includes indication information used to indicate aphysical resource block number of the control channel resource set; andthe obtaining, by a terminal device, position offset informationincludes: determining, by the terminal device, the position offsetinformation according to the indication information used to indicate thephysical resource block number.

According to this solution, all control channel resources use a samephysical resource block number, and a reference point of the physicalresource block number may be notified by a MIB or RMSI, and further, theterminal device obtains the unified physical resource block number infrequency domain according to a same frequency domain reference point.Therefore, first sequences determined for control channel resource setsincluding the same physical resource block number are the same, so thatfirst sequences of control channel resource sets with overlappingresources are the same. Therefore, orthogonal reuse by a plurality ofusers, that is, orthogonal MU-MIMO, is enabled.

In a possible design, the method further includes: receiving, by theterminal device, a MIB sent by a network device, where the MIB includesindication information used to indicate an eleventh relative position ofthe control channel resource set relative to a reference point of abroadcast channel carrying the MIB; and obtaining, by the terminaldevice, the second sequence from the reference signal sequence accordingto the indication information, where the second sequence is a subset ofthe reference signal sequence. In the method, the MIB does not need tocarry indication information of the frequency domain reference point.Therefore, indication signaling overheads of the MIB are reduced. Inaddition, the frequency domain reference point is indicated by RMSIoccupying more resources. Therefore, bandwidth configurations are moreflexible, fragments of the bandwidth in use are reduced, and spectrumutilization is improved. The second sequence is used for a referencesignal included in a first control channel resource set configured bythe MIB, and the first control channel resource set includes a commonsearch space, and mainly carries control information for scheduling theRMSI. The foregoing first sequence is used for the control channelresource set configured by RRC, and the first control channel resourceset includes a common search space and/or a user specific search space,and mainly carries control information for scheduling data.

According to a second aspect, an embodiment of this application providesa method for obtaining a reference signal. The method includes:obtaining, by a network device, position offset information; obtaining afirst sequence based on the position offset information.

In a possible design, the method further includes: generating, by thenetwork device, a reference signal sequence; and obtaining the firstsequence from the reference signal sequence based on the position offsetinformation, where the first sequence is a subset of the referencesignal sequence.

In a possible design, the method further includes: sending, by thenetwork device, a MIB to a terminal device, where the MIB includesindication information of a first relative position and indicationinformation of a second relative position, the first relative positionis a position of a reference point of a broadcast channel carrying theMIB, relative to a frequency domain reference point, the second relativeposition is a relative position of the control channel resource setrelative to the reference point of the broadcast channel, and theindication information of the first relative position and the indicationinformation of the second relative position are used to indicate theposition offset information.

In a possible design, the method further includes: receiving, by theterminal device, a MIB sent by a network device, where the MIB includesindication information of a third relative position, the third relativeposition is a position of a reference point of a broadcast channelcarrying the MIB, relative to a frequency domain reference point, theindication information of the third relative position is used with afourth relative position to indicate the position offset information,the fourth relative position is a relative position of the controlchannel resource set relative to the reference point of the broadcastchannel, and the fourth relative position is configured or preset.

In a possible design, the method further includes: sending, by thenetwork device, a master information block MIB to a terminal device;where the MIB includes indication information used to indicate eighthrelative position information of the control channel resource setrelative to a frequency domain reference point, and the indicationinformation of the eighth relative position information is used toindicate the position offset information.

In a possible design, the method further includes: sending, by thenetwork device, configuration information of a bandwidth to a terminaldevice, where the bandwidth is a part of a system bandwidth, theconfiguration information includes indication information of a fifthrelative position, the fifth relative position is a relative position ofa bandwidth comprising the control channel resource set relative to afrequency domain reference point, and the indication information of thefifth relative position is used to indicate the position offsetinformation.

In a possible design, the method further includes: sending, by thenetwork device, configuration information of a bandwidth to a terminaldevice, where the bandwidth is a part of a system bandwidth, theconfiguration information includes indication information of a sixthrelative position and indication information of a seventh relativeposition, the sixth relative position is a relative position of abandwidth comprising the control channel resource set relative to areference point frequency domain position of a broadcast channelcarrying a MIB, the seventh relative position is a position of thereference point of the broadcast channel carrying the MIB, relative to afrequency domain reference point, and the indication information of thesixth relative position and the indication information of the seventhrelative position are used to indicate the position offset information.

In a possible design, the method further includes: sending, by thenetwork device, configuration information of the control channelresource set to a terminal device, where the configuration informationof the control channel resource set includes indication information usedto indicate the position offset information. The indication informationused to indicate the position offset information includes indicationinformation used to indicate a physical resource block number of thecontrol channel resource set.

In a possible design, the method further includes: sending, by thenetwork device, a master information block MIB, where the MIB includesindication information used to indicate an eleventh relative position ofthe control channel resource set relative to a reference point of abroadcast channel carrying the MIB.

According to a third aspect, an embodiment of this application providesan apparatus for obtaining a reference signal, where the apparatus has afunction for implementing actions of the terminal device in theforegoing method designs. The function may be implemented by hardware,or may be implemented by corresponding software executed by hardware.The hardware or software includes one or more modules corresponding tothe foregoing function.

In a possible design, a structure of the terminal device includes aprocessor, where the processor is configured to: obtain position offsetinformation, and obtain a first sequence based on the position offsetinformation.

According to a fourth aspect, an embodiment of this application providesan apparatus for obtaining a reference signal. The apparatus has afunction for implementing actions of the network device in the foregoingmethod designs. The function may be implemented by hardware, or may beimplemented by corresponding software executed by hardware. The hardwareor software includes one or more modules corresponding to the foregoingfunction.

In a possible design, a structure of the apparatus includes a processor,where the processor is configured to support the network device inperforming corresponding functions in the foregoing method. The networkdevice may further include a memory. The memory is coupled with theprocessor. The memory stores a program instruction and data required bythe network device.

In a possible design, in any method in the first to the fourth aspects,the configuration information of the control channel resource setincludes at least one of a random access response (RAR) and radioresource control (RRC) signaling, and the control channel resource setincludes a type-1 common search space (CSS) and/or a terminal specificsearch space (USS).

In any one of the first to the fourth aspects, the frequency domainreference point is a system carrier bandwidth boundary or a centerfrequency domain position, or is a candidate position of a channelraster, where the candidate position of the channel raster is acandidate subcarrier position within the system carrier bandwidth, andthe candidate subcarrier position is a predefined position; and thereference point of the broadcast channel is a center frequency domainposition or a boundary of a resource on which the reference point of thebroadcast channel is located.

According to a fifth aspect, an embodiment of this application providesa method for obtaining a reference signal, where the method includes:obtaining, by a terminal device, an initial value for generating a firstsequence or length information of a first sequence; generating the firstsequence based on the initial value or the length information of thefirst sequence.

In a possible design, the method further includes: receiving, by theterminal device, a MIB, where the MIB includes indication informationused to indicate a time-frequency resource occupied by the controlchannel resource set; and determining a length of the first sequenceaccording to the indication information used to indicate thetime-frequency resource occupied by the control channel resource set.

In a possible design, the obtaining, by a terminal device, an initialvalue for generating a first sequence includes: obtaining, by theterminal device, one or more of a synchronization signal, a broadcastchannel scrambling sequence, a broadcast channel reference signal, orbroadcast information that includes the initial value for generating thefirst sequence.

According to the solution provided by the fifth aspect, the MIB does notinclude indication information of a frequency domain reference point,and therefore, indication signaling overheads of the MIB can be reduced.Therefore, the terminal device cannot obtain a position relative to thefrequency domain reference point, and can only directly generate areference signal sequence, or truncate the first sequence from a centerposition of a reference signal sequence. Because a size of an initialaccess bandwidth is limited, it is less possible that control channelresource sets sent in different frequency bands in frequency domainoverlap each other in frequency domain. Therefore, reuse by a pluralityof users is impossible. However, a terminal device receiving RMSI canobtain the first sequence according to a reference point configured bythe RMSI, and orthogonal reuse by a plurality of users, that is,MU-MIMO, can be implemented in an overlapping resource region between aplurality of control channel resource sets.

According to a sixth aspect, an embodiment of this application providesa method for obtaining a reference signal, where the method includes:obtaining, by a network device, an initial value for generating a firstsequence or length information of a first sequence; generating the firstsequence based on the initial value or the length information of thefirst sequence.

In a possible design, the method further includes: sending, by thenetwork device, a MIB to a terminal device, where the MIB includesindication information used to indicate a time-frequency resourceoccupied by the control channel resource set.

In a possible design, the method further includes: sending, by thenetwork device, one or more of a synchronization signal, a broadcastchannel scrambling sequence, a broadcast channel reference signal, orbroadcast information that includes the initial value for generating thefirst sequence to the terminal device.

According to a seventh aspect, an embodiment of this applicationprovides an apparatus for obtaining a reference signal, where theapparatus has a function for implementing actions of the terminal devicein the foregoing method designs. The function may be implemented byhardware, or may be implemented by corresponding software executed byhardware. The hardware or software includes one or more modulescorresponding to the foregoing function. The module may be softwareand/or hardware.

In a possible design, the terminal device includes a processor,configured to: obtain an initial value for generating a first sequenceor length information of the first sequence; generate the first sequencebased on the initial value or the length information of a firstsequence; and demodulate, by using the first sequence, a control channelsignal carried in a control channel resource set, to obtain downlinkcontrol information.

According to an eighth aspect, an embodiment of this applicationprovides an apparatus for obtaining a reference signal, where theapparatus has a function for implementing actions of the network devicein the foregoing method designs. The function may be implemented byhardware, or may be implemented by corresponding software executed byhardware. The hardware or software includes one or more modulescorresponding to the foregoing function.

In a possible design, a structure of the apparatus includes a processorand a transmitter, where the processor is configured to support anetwork device in performing corresponding functions in the foregoingmethod. The apparatus may further include a memory. The memory iscoupled with the processor. The memory stores a program instruction anddata required by the apparatus.

According to a ninth aspect, an embodiment of this application providesa computer readable storage medium, where the computer readable storagemedium stores a computer software instruction used by a terminal device,and the instruction is used to execute the method designed in the firstaspect.

According to a tenth aspect, an embodiment of this application providesa readable storage medium, where the computer readable storage mediumstores an instruction of a network device, and the instruction is usedto execute the program designed in the second aspect.

According to an eleventh aspect, an embodiment of this applicationprovides a computer readable storage medium, where the computer readablestorage medium stores an instruction of a terminal device, and theinstruction is used to execute the program designed in the fifth aspect.

According to a twelfth aspect, an embodiment of this applicationprovides a readable storage medium, where the computer readable storagemedium stores an instruction of a network device, and the instruction isused to execute the program designed in the sixth aspect.

According to a thirteenth aspect, an embodiment of this applicationprovides a communications apparatus, including: a memory, where thememory is configured to store computer executable program code; and aprocessor, where when the processor executes the instruction, theapparatus is configured to implement the method according to the firstaspect.

According to a fourteenth aspect, an embodiment of this applicationprovides a communications apparatus, including: a memory, where thememory is configured to store computer executable program code; and aprocessor, where when the processor executes the instruction, theapparatus is configured to implement the method according to the secondaspect.

According to a fifteenth aspect, an embodiment of this applicationprovides a communications apparatus, including: a memory, where thememory is configured to store computer executable program code; and aprocessor, where when the processor executes the instruction, theapparatus is configured to implement the method according to the fifthaspect.

According to a sixteenth aspect, an embodiment of this applicationprovides a communications apparatus, including: a memory, configured tostore computer executable program code; and a processor, where when theprocessor executes the instruction, the apparatus is configured toimplement the method according to the sixth aspect.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic diagram of an architecture of a communicationsnetwork according to an embodiment of this application;

FIG. 2 is a schematic flowchart of a method for obtaining a referencesignal according to an embodiment of this application;

FIG. 3 is a schematic diagram of a correspondence between a firstrelative position and a reference point of a broadcast channel in amanner 1 according to an embodiment of this application;

FIG. 4 is a schematic diagram of a correspondence between a secondrelative position and a control channel resource set in a manner 1according to an embodiment of this application;

FIG. 5 is a schematic diagram of a correspondence between a firstrelative position and a second relative position in a manner 1 accordingto an embodiment of this application;

FIG. 6 is a schematic diagram of a correspondence between a controlchannel resource set and a fourth relative position in a manner 2according to an embodiment of this application;

FIG. 7 is a schematic diagram for indicating a correspondence between athird relative position and a fourth relative position in a manner 2according to an embodiment of this application;

FIG. 8 is a schematic diagram of a correspondence between an offsetposition 4 and a control channel resource set in a manner 3 according toan embodiment of this application;

FIG. 9 is a schematic diagram of a correspondence between a bandwidthand a fifth relative position in a manner 4 according to an embodimentof this application;

FIG. 10 is a schematic diagram of another correspondence between abandwidth and a fifth relative position in a manner 4 according to anembodiment of this application;

FIG. 11 is a schematic diagram of another correspondence between abandwidth and a fifth relative position in a manner 4 according to anembodiment of this application;

FIG. 12 is a schematic diagram of another correspondence between abandwidth and a fifth relative position in a manner 4 according to anembodiment of this application;

FIG. 13 is a schematic diagram of a correspondence between a referencepoint of a broadcast channel and a seventh relative position in a manner5 according to an embodiment of this application;

FIG. 14 is a schematic diagram of a correspondence between a sixthrelative position and a seventh relative position in a manner 5according to an embodiment of this application;

FIG. 15 is a schematic diagram of a correspondence between a controlchannel resource set and a physical resource block number in a manner 6according to an embodiment of this application;

FIG. 16 is a schematic diagram of another correspondence between acontrol channel resource set and a physical resource block number in amanner 6 according to an embodiment of this application;

FIG. 17 is a schematic flowchart of another method for obtaining areference sequence according to an embodiment of this application;

FIG. 18 is a schematic flowchart of another method for obtaining areference sequence according to an embodiment of this application;

FIG. 19 is a schematic flowchart of another method for obtaining areference signal according to an embodiment of this application;

FIG. 20 is a schematic diagram of a sequence truncated from a referencesignal sequence of a reference point of a broadcast channel;

FIG. 21 is a schematic diagram of a reference signal sequence mappingaccording to an embodiment of this application;

FIG. 22 is another schematic diagram of a reference signal sequencemapping according to an embodiment of this application;

FIG. 23 is an apparatus for obtaining a reference signal according to anembodiment of this application;

FIG. 24 is another apparatus for obtaining a reference signal accordingto an embodiment of this application;

FIG. 25 is another apparatus for obtaining a reference signal accordingto an embodiment of this application;

FIG. 26 is another apparatus for obtaining a reference signal accordingto an embodiment of this application; and

FIG. 27 is another apparatus for obtaining a reference signal accordingto an embodiment of this application.

DESCRIPTION OF EMBODIMENTS

To make the objectives, technical solutions, and advantages of thisapplication clearer, the following describes the technical solutions ofthe embodiments of this application in more detail with reference toembodiments and accompanying drawings.

The technical solutions according to embodiments of this application areclearly described in the following with reference to the accompanyingdrawings. Apparently, the described embodiments are merely some but notall of the embodiments of this application. All other embodimentsobtained by a person of ordinary skill in the art based on theembodiments of this application without creative efforts shall fallwithin the protection scope of this application.

Network architectures and application scenarios described in theembodiments of this application are intended to describe the technicalsolutions of the embodiments of this application more clearly, and donot constitute any limitation to the technical solutions provided by theembodiments of this application. A person of ordinary skill in the artmay know that, with evolution of the network architectures and emergenceof new service scenarios, the technical solutions provided by theembodiments of this application are also applicable to similar technicalproblems.

The technical solutions of this application may be applied to variouscommunications systems that are based on non-orthogonal multiple accesstechnologies, for example, a sparse code multiple access (SCMA) system,and a low density signature (LDS) system. Certainly, the SCMA system andthe LDS system may also be referred to as other names. Further, thetechnical solutions of the embodiments of this application may beapplied to a multicarrier transmission system using a non-orthogonalmultiple access technology, for example, a system using a non-orthogonalmultiple access technology, orthogonal frequency division multiplexing(OFDM), filter bank multicarrier (FBMC), generalized frequency, divisionmultiplexing (GFDM), or filtered orthogonal frequency divisionmultiplexing (F-OFDM).

A terminal device in this application may be an access terminal, asubscriber unit, a subscriber station, a mobile station, a mobilestation, a remote station, a remote terminal, a mobile device, a userterminal, a terminal, a wireless communications device, a user agent, ora user apparatus. The access terminal may be a cellular phone, acordless phone, a Session Initiation Protocol (SIP) phone, a wirelesslocal loop (WLL) station, a personal digital assistant (PDA), a handhelddevice having a wireless communication function, a computing device,another processing device connected to a wireless modem, an in-vehicledevice, a wearable device, a terminal device in a future 5G network, aterminal device in a future evolved public land mobile network (PLMN),or the like. This is not limited in the embodiments of this application.

A network device in this application may be a device for communicatingwith a terminal device. The network device may be a base transceiverstation (BTS) in a global system for mobile communications (GSM) systemor a code division multiple access (CDMA) system, or may be a NodeB(NodeB, NB) in a wideband code division multiple access (WCDMA) system,or may be an evolved NodeB (evolved NodeB, eNB or eNodeB) in an LTEsystem, or may be a radio controller in a cloud radio access network(CRAN) scenario; or the network device may be a relay station, an accesspoint, an in-vehicle device, a wearable device, a network device in afuture 5G network, a network device in a future evolved PLMN network, orthe like. This is not limited in the embodiments of this application.

Referring to FIG. 1, FIG. 1 is a schematic diagram of an architecture ofa communications network according to an embodiment of this application.As shown in FIG. 1, the communications system may include a terminaldevice 10 and a network device 20. The network device 20 is configuredto provide a communications service for the terminal device 10 andaccess a core network. The terminal device 10 accesses the network bydetecting a synchronization signal or a broadcast signal or the likesent by the network device 20, so as to communicate with the networkdevice. Arrows shown in FIG. 1 may indicate uplink transmission and/ordownlink transmission performed by using radio links between theterminal device 10 and the network device 20. For ease of description,only one terminal device is used as an example for description inFIG. 1. However, the network architecture includes but is not limited toone terminal device.

In this application, the term “symbol” includes but is not limited to anorthogonal frequency division multiplexing (OFDM) symbol, a sparse codemultiple access technology (SCMA) symbol, a filtered orthogonalfrequency division multiplexing (F-OFDM) symbol, or a non-orthogonalmultiple access (NOMA) symbol, which may be determined according to anactual situation. Details are not described herein.

In this application, the term “subframe” is a time-frequency resourceoccupying a whole system bandwidth in frequency domain or atime-frequency resource element of fixed duration in time domain, forexample, 1 millisecond.

In this application, the term “timeslot” is a basic time-frequencyresource element, and occupies 7 or 14 consecutive OFDM symbols in timedomain.

In this application, the term “subcarrier width” is a smallestgranularity in frequency domain. For example, in the LTE network, asubcarrier width of a subcarrier is 15 kHz; in 5G, a subcarrier widthmay be 15 kHz, 30 kHz, or 60 kHz.

In this application, the term “physical resource block” is P consecutivesubcarriers occupied in frequency domain, and resources occupied in timedomain are Q consecutive OFDM symbols. P and Q are natural numbers thatare greater than or equal to 1. For example, a physical resource blockmay occupy 12 consecutive subcarriers in frequency domain, and mayoccupy 7 consecutive OFDM symbols in time domain, where P=12, and Q=7;or P=12, and Q=14; or P=12, and Q=1.

Physical resource block number in this application: A physical resourceblock number corresponds to a frequency domain position of an actualphysical resource block. For example, if the physical resource blocknumber is n, a set of 12 corresponding consecutive subcarrier numbers infrequency domain is {n, n+1, n+2, n+3, n+5, n+6, n+7, n+8, n+9, n+10,n+11}. The physical resource block number may be a number of a physicalresource block included in a system carrier bandwidth, or the physicalresource block number is a number of a physical resource block in asubband within a system carrier bandwidth.

In this application, the term “resource element group” is P consecutivesubcarriers occupied in frequency domain, and resources occupied in timedomain are one consecutive OFDM symbol. P is a natural number that isgreater than 1. For example, a resource element group may occupy 12consecutive subcarriers in frequency domain. Specifically, P=12.

In this application, the term “control channel element” corresponds to aplurality of resource element groups, and a quantity of resource elementgroups corresponding to a control channel element is fixed, for example,6.

In this application, the term “control channel resource set” is atime-frequency resource carrying a control channel, including one ormore consecutive or discrete time-frequency resource blocks in timedomain and/or frequency domain.

In this application, the term “position offset information” isindication information used to determine an offset of a physical channelrelative to a reference point. Specifically, an offset of atime-frequency resource on which the physical channel is located;relative to the reference point may be obtained based on the positionoffset information, and a unit of the offset may be a quantity ofphysical resource blocks, a quantity of subcarriers, a quantity of REGs,or the like.

In this application, ordinal numbers such as “first”, “second”, “third”,“fourth”, “fifth”, “sixth”, “seventh”, “eighth”, and “ninth” are usedfor distinguishing a plurality of objects, instead of limiting asequence, a time sequence, priorities, importance, or the like of theplurality of objects.

In this application, “a frequency domain reference point” may be asystem carrier bandwidth boundary or a center frequency domain position(for example; a center frequency), for example, a smallest subcarrierwithin a system carrier bandwidth, a largest subcarrier within a systemcarrier bandwidth, or a center subcarrier within a system carrierbandwidth; or a frequency domain reference point may be a candidateposition of a channel raster, where the candidate position of thechannel raster corresponds to a subcarrier position of the channelraster within a system bandwidth, and the subcarrier position of thechannel raster is a predefined position. For example, within the systemcarrier bandwidth, a subcarrier position of one channel raster isincluded at an interval of 300 kHz.

In this application, “a reference point of a broadcast channel” may be acenter frequency domain position or a boundary of a resource on whichthe broadcast channel is located, for example, a smallest subcarrier ofthe resource on which the broadcast channel is located, a largestsubcarrier of the resource on which the broadcast channel is located, ora center subcarrier of the resource on which the reference point of thebroadcast channel is located.

In this application, “a relative position of a control channel resourceset relative to a reference point of a broadcast channel or a frequencydomain reference point” includes a position of a frequency domainboundary or a frequency domain center position of the control channelresource set relative to the reference point of the broadcast channel orthe frequency domain reference point, where the frequency domainboundary includes a smallest subcarrier or a largest subcarrier in thecontrol channel resource set.

“The relative position of a bandwidth relative to a reference point of abroadcast channel or a frequency domain reference point” includes aposition of a frequency domain boundary or a frequency domain centerposition of the bandwidth relative to the reference point of thebroadcast channel or the frequency domain reference point, where thefrequency domain boundary includes a smallest subcarrier or a largestsubcarrier in the control channel resource set.

FIG. 2 is a schematic flowchart of a method for obtaining a referencesignal according to an embodiment of this application. As shown in FIG.2, the method includes the following parts.

Part 201: A network device obtains position offset information.

Part 202: The network device obtains a first sequence based on theposition offset information.

In an example, that the network device obtains a first sequence based onthe position offset information includes: the network device obtains thefirst sequence based on the position offset information, or the networkdevice generates the first sequence based on the position offsetinformation.

In another example, the method further includes: the network devicegenerates a reference signal sequence. It should be especiallyemphasized that no sequence exists between the generating a referencesignal sequence and part 201. Specifically, the reference signalsequence may be generated first, and then the position offsetinformation is obtained; or the position offset information is obtainedfirst, and then the reference signal sequence is generated.

That the network device obtains a first sequence based on the positionoffset information includes: the network device obtains the firstsequence from the reference signal sequence based on the position offsetinformation, where the first sequence is a subset of the referencesignal sequence, and the position offset information is a position of atleast one value of the first sequence in the reference signal sequence.

In another example, that a network device obtains position offsetinformation includes: the network device may determine the positionoffset information according to a position of a resource element formapping the first sequence. The control channel resource set includesthe resource element.

Part 203: The network device maps the first sequence to a resourceelement carrying a reference signal in a control channel resource set.

In an example, the network device sends a MIB to a terminal device,where the MIB includes indication information of a first relativeposition and indication information of a second relative position, thefirst relative position is a position of a reference point of abroadcast channel carrying the MIB, relative to a frequency domainreference point, the second relative position is a relative position ofthe control channel resource set relative to the reference point of thebroadcast channel, and the indication information of the first relativeposition and the indication information of the second relative positionare used to indicate the position offset information.

In another example, the network device sends a MIB to a terminal device,where the MIB includes indication information of a third relativeposition, the third relative position is a position of a reference pointof a broadcast channel carrying the MIB, relative to a frequency domainreference point, the indication information of the third relativeposition is used with a fourth relative position to indicate theposition offset information, the fourth relative position is a relativeposition of the control channel resource set relative to the referencepoint of the broadcast channel, and the fourth relative position isconfigured or preset.

In another example, the network device sends a master information blockMIB to a terminal device, where the MIB includes indication informationused to indicate eighth relative position information of the controlchannel resource set relative to a frequency domain reference point, andthe indication information of the eighth relative position informationis used to indicate the position offset information.

In another example, the network device sends configuration informationof a bandwidth to a terminal device, where the configuration informationincludes indication information of a fifth relative position, the fifthrelative position is a relative position of a system bandwidth subset ofthe control channel resource set relative to a frequency domainreference point, and the indication information of the fifth relativeposition is used to indicate the position offset information.

In another example, the network device sends configuration informationof a bandwidth to a terminal device, where the configuration informationincludes indication information of a sixth relative position andindication information of a seventh relative position, the sixthrelative position is a relative position of a bandwidth comprising thecontrol channel resource set relative to a reference point frequencydomain position of a broadcast channel carrying a MIB, the seventhrelative position is a position of the reference point of the broadcastchannel carrying the MIB, relative to a frequency domain referencepoint, and the indication information of the sixth relative position andthe indication information of the seventh relative position are used toindicate the position offset information.

In another example, the network device sends configuration informationof the control channel resource set to a terminal device, where theconfiguration information of the control channel resource set includesindication information used to indicate the position offset information.For example, the indication information used to indicate the positionoffset information includes indication information used to indicate aphysical resource block number of the control channel resource set.

In another example, that a network device obtains position offsetinformation includes: determining the position offset informationaccording to a position of a resource element for mapping the firstsequence, where the control channel resource set includes the resourceelement for mapping the first sequence.

In another example, a complex value modulation symbol corresponding tothe first sequence is obtained according to the first sequence. Thenetwork device maps the complex value modulation symbol to a predefinedcontrol channel reference signal resource element, and sends the controlchannel.

Part 204: A terminal device obtains position offset information.

In an example, the terminal device may obtain the position offsetinformation in any one of the following manners:

Manner 1: The terminal device receives a master information block MIBsent by the network device, where the MIB includes indicationinformation used to indicate a first relative position and indicationinformation used to indicate a second relative position, the firstrelative position is a position of a reference point of a broadcastchannel carrying the MIB, relative to a frequency domain referencepoint, and the second relative position is a relative position of thecontrol channel resource set relative to the reference point of thebroadcast channel; and that a terminal device obtains position offsetinformation includes: the terminal device determines the position offsetinformation according to the first relative position indicated by theindication information of the first relative position and the secondrelative position indicated by the indication information of the secondrelative position.

According to the solution provided in the manner 1, when referencepoints of a plurality of broadcast channels are sent in differentfrequency domain positions, reference signals used by control channelresources configured for reference points of different broadcastchannels are selected from a same sequence. In addition, even if aplurality of control channel resources overlap each other, a same firstsequences is used in an overlapping region, and further, resource reuseby a plurality of users, for example, orthogonal MU-MIMO, can beimplemented in the overlapping resource region. In addition, the MIBincludes the position offset information of the control channelresources. This is advantageous to forward compatibility, and canflexibly avoid interference from a signal sent by a neighboring cell onthe control channel resources.

FIG. 3 is a schematic diagram of a correspondence between a firstrelative position and a reference point of a broadcast channel in themanner 1. As shown in FIG. 3, a reference point of each broadcastchannel corresponds to a first relative position.

For example, the first relative position may be an offset of a quantityof physical resource blocks, of the reference point of the broadcastchannel relative to the frequency domain reference point. In thisembodiment, only the quantity of offset physical resource blocks is usedas an example for indicating the offset. An actual offset may bepredefined as other resource units, and is not limited herein.

In the manner 1, the terminal device receives the master signal blockMIB sent by the network device, where the MIB includes the indicationinformation used to indicate the first relative position of thereference point of the broadcast channel carrying the MIB, relative tothe frequency domain reference point. For example, for a value of thefirst relative position, refer to Table 1. For example, indicationinformation of a reference point 2 of a broadcast channel is 001, and afirst relative position 2 is +N^(Offset) _(RB).

TABLE 1 Reference point of a Indication First relative broadcast channelinformation position 0 000 0 2 001  +N^(Offset) _(RB) 4 010 +2N^(Offset)_(RB) 1 011  −N^(Offset) _(RB) 3 100 −2N^(Offset) _(RB)

For example, indication information of a reference point 1 of abroadcast channel included in the MIB is {011}, and it may bedetermined, according to a correspondence between the reference point ofthe broadcast channel, the indication information, and the firstrelative position, that a first relative position 2 corresponding to thereference point 1 of the broadcast channel is {−N^(Offset) _(RB)}.Similarly, indication information of a reference point 2 of a broadcastchannel is {001}, and a first relative position 4 is {+N^(Offset)_(RB)}; indication information corresponding to a reference point 3 of abroadcast channel is {100}, and a first relative position 1 is{−2N^(Offset) _(RB)}; indication information corresponding to areference point 4 of a broadcast channel is {010}, and a first relativeposition 5 is {+2N^(Offset) _(RB)}; indication information correspondingto a reference point 0 of a broadcast channel is {100}, and a firstrelative position 3 is {0}.

For example, the correspondence between the reference point of thebroadcast channel, the indication information, and the first relativeposition may be predefined by the network device and the terminaldevice, or may be specified by a protocol, or may be preconfigured. Thisis not specifically limited in this application, and shall fall withinthe protection scope of this application as long as the correspondencebetween the reference point of the broadcast channel, the indicationinformation, and the first relative position can be reflected.

For example, the MIB sent by the network device and received by theterminal device further includes the indication information used toindicate the second relative position of the control channel resourceset relative to the reference point of the broadcast channel. FIG. 4 isa schematic diagram of a correspondence between a control channelresource set and a second relative position in the manner 1. As shown inFIG. 4, a center subcarrier of a reference point 0 of a broadcastchannel is located on a center frequency, and the second relativeposition is a relative position of the control channel resource setrelative to the reference point 0 of the broadcast channel.

As shown in Table 2, indication information corresponding to the controlchannel resource set 0 included in the MIB is 000, and a second relativeposition is −2N^(CORESET_offset) _(RB). Indication informationcorresponding to a control channel resource set 1 included in the MIB is001, and a second relative position is −2N^(CORESET_offset) _(RB). Basedon a correspondence between the reference point of the broadcastchannel, the indication information, and the second relative position, aresource position offset of the control channel resource set relative toa center position of the reference point of the broadcast channel may bedetermined according to the indication information.

TABLE 2 Control channel Indication Second relative resource setinformation position 0 000 −2N^(CORESET) ^(—) ^(offset) _(RB) 1 001 −N^(CORESET) ^(—) ^(offset) _(RB) 2 010 0 3 011  +N^(CORESET) ^(—)^(offset) _(RB) 4 100 +2N^(CORESET) ^(—) ^(offset) _(RB)

FIG. 5 is a schematic diagram of a correspondence between a firstrelative position and a second relative position in the manner 1. Asshown in FIG. 5, position offset information of a control channelresource set 4 is determined according to a first relative position 4and a second relative position 4, where the first relative position 4 is+N^(Offset) _(RB), and the second relative position 4 is+2N^(CORESET_offset) _(RB). Therefore, an offset position of the controlchannel resource set 4 is N^(Offset) _(RB)+2N^(CORESET_offset) _(RB).

It should be especially emphasized that the position offset informationmay be obtained according to the first relative position and the secondrelative position by using any one of the following methods: forexample, performing one or more of summation, deduction, multiplication,or division processing on the first relative position and the secondrelative position to determine the position offset information.

Further, the terminal device obtains a first sequence based on theoffset position (N^(Offset) _(RB)+2N^(CORESET_offset) _(RB)).

For example, that the terminal device obtains a first sequence based onthe position offset information includes:

A. The terminal device may generate a reference signal sequence by usinga formula (1).

$\begin{matrix}{{{r(m)} = {{\frac{1}{\sqrt{2}}\left( {1 - {2 \cdot {c\left( {2m} \right)}}} \right)} + {j\frac{1}{\sqrt{2}}\left( {1 - {2 \cdot {c\left( {{2m} + 1} \right)}}} \right)}}},{m = 0},1,\ldots\;,{{n_{RE}^{RB} \cdot N_{RB}^{\max,{DL}}} - 1}} & (1)\end{matrix}$

where N^(max,DL) _(RB) indicates a maximum quantity of a physicalresource blocks included in a system carrier bandwidth, and n^(RB) _(RE)is a quantity of resource elements included in each physical resourceblock and used for mapping a reference signal.

B. The terminal device obtains the first sequence from the referencesignal sequence r based on the position offset information.

For example, according to a length N_(RS) of the first sequence in theoffset position, a value range of the first sequence is k=0, 1, 2, . . ., N_(RS)-1, and the obtained first sequence may be r (k+offsetposition), where an offset indicated by the offset position isN^(Offset) _(RB)+2N^(CORESET_offset) _(RB). To be specific, the positionoffset in formation=N^(Offset) _(RB)+2N^(CORESET_offset) _(RB).

For example, the correspondence between the reference point of thebroadcast channel, the indication information, and the first relativeposition or the second relative position may be predefined by thenetwork device and the terminal device, or may be specified by aprotocol, or may be preconfigured. This is not specifically limited inthis application, and shall fall within the protection scope of thisapplication as long as the correspondence between the reference point ofthe broadcast channel, the indication information, and the firstrelative position can be reflected.

Manner 2: The terminal device receives a master signal block MIB sent bythe network device, where the MIB includes indication information usedto indicate a third relative position, and the third relative positionis a position of a reference point of a broadcast channel carrying theMIB, relative to a frequency domain reference point; and that a terminaldevice obtains position offset information includes: the terminal devicedetermines the position offset information according to the thirdrelative position indicated by the indication information of the thirdrelative position and a fourth relative position, where the fourthrelative position is a relative position of the control channel resourceset relative to the reference point of the broadcast channel, and thefourth relative position is configured or preset.

According to the solution in the manner 2, when reference points of aplurality of broadcast channels are sent in different frequency domainpositions, reference signals used by control channel resourcesconfigured for reference points of different broadcast channels areselected from a same sequence. In addition, even if a plurality ofcontrol channel resources overlap each other, a same first sequences isused in an overlapping region, and further, resource reuse by aplurality of users, for example, orthogonal MU-MIMO, can be implementedin the overlapping resource region.

It should be especially noted that, for a manner of indicating the thirdrelative position in the manner 2, refer to the manner of indicating thefirst relative position in the manner 1. Details are not described againherein.

It should be especially emphasized that the position offset informationmay be obtained according to the third relative position and the fourthrelative position by using any one of the following methods: forexample, performing one or more of summation, deduction, multiplication,or division processing on the third relative position and the fourthrelative position to determine the position offset information.

FIG. 6 is a schematic diagram of a correspondence between a controlchannel resource set and a fourth relative position in the manner 2. Asshown in FIG. 6, the fourth relative position is a relative position ofthe control channel resource set relative to a reference point 0 of abroadcast channel. For example, a position of a center subcarrier of aresource of the control channel resource set is the same as that of acenter subcarrier of the reference point of the broadcast channel. Inaddition, the fourth relative position is configured or preset.

It should be especially noted that the position of the control channelresource set relative to the reference point of the broadcast channel isfixed in the manner 2, but whether a size of a time-frequency resourceincluded in the control channel resource set is variable is not limited.

FIG. 7 is a schematic diagram of a correspondence between a thirdrelative position and a fourth relative position in the manner 2. Asshown in FIG. 7, position offset information of the control channelresource set 4 is determined according to a third relative position 4and a fourth relative position 4. Assuming that indication informationincluded in the MIB is 001, according to Table 1 in the manner 1, it canbe known that the third relative position 4 is +N^(Offset) _(RB), and aresource position of the control channel resource set relative to thereference point of the broadcast channel is predefined and is 0, thatis, the fourth relative position is predefined as a center position ofthe reference point of the broadcast channel. Therefore, position offsetinformation of the control channel resource set 4 is +N^(Offset) _(RB).

For a manner of obtaining the first sequence by the terminal devicebased on the position offset information (+N^(Offset) _(RB)), refer to amanner of obtaining the first sequence based on the position offsetinformation in the manner 1. Details are not described again herein.

Manner 3: The terminal device receives a master information block MIB,where the MIB includes indication information used to indicate eighthrelative position information of the control channel resource setrelative to a frequency domain reference point; and that a terminaldevice obtains position offset information includes: the terminal devicedetermines the position offset information according to the eighthrelative position indicator by the indication information of the eighthrelative position.

According to the solution provided in the manner 3, when referencepoints of a plurality of broadcast channels are sent in differentfrequency domain positions, reference signals used by control channelresources configured for reference points of different broadcastchannels are selected from a same sequence. In addition, even if aplurality of control channel resources overlap each other, a same firstsequences is used in an overlapping region, and further, resource reuseby a plurality of users, for example, orthogonal MU-MIMO, can beimplemented in the overlapping resource region. In addition, a referenceposition of a control channel relative to a reference point of abroadcast channel and position information of the reference point of thebroadcast channel relative to the frequency domain reference point canbe jointly encoded. This improves coding efficiency and reducesindication signaling overheads.

For example, the terminal device receives the indication information ofthe eighth relative position. For example, the indication information is011, as shown in Table 3, and the indication information 011 representsthat an eighth relative position 4 of the control channel resource set 3is +N^(CORESET_offset) _(RB).

TABLE 3 Control channel Indication Eighth relative resource setinformation position 0 000 −2N^(CORESET) ^(—) ^(offset) _(RB) 1 001 −N^(CORESET) ^(—) ^(offset) _(RB) 2 010 0 3 011  +N^(CORESET) ^(—)^(offset) _(RB) 4 100 +2N^(CORESET) ^(—) ^(offset) _(RB)

FIG. 8 is a schematic a correspondence between an eighth relativeposition 4 and a control channel resource set in the manner 3. As shownin FIG. 8, according to Table 4, it can be known that an eighth relativeposition corresponding to a control channel resource set 3 is+N^(CORESET_offset) _(RB).

The terminal device determines, according to the eighth relativeposition, that the position offset information is (+N^(CORESET_offset)_(RB)). For a manner of obtaining the first sequence based on theposition offset information, refer to the manner of obtaining the firstsequence based on the position offset information in the manner 1.Details are not described again herein.

For example, the correspondence between the control channel resourceset, the indication information, and the eighth relative position may bepredefined by the network device and the terminal device, or may bespecified by a protocol, or may be preconfigured. This is notspecifically limited in this application, and shall fall within theprotection scope of this application as long as the correspondencebetween the control channel resource set, the indication information,and the eighth relative position can be reflected.

Manner 4: The terminal device receives configuration information of abandwidth part, where the configuration information includes indicationinformation of a fifth relative position, and the fifth relativeposition is a relative position of a bandwidth part comprising thecontrol channel resource set relative to a frequency domain referencepoint; and that a terminal device obtains position offset informationincludes: the terminal device determines the position offset informationaccording to the fifth relative position indicated by the indicationinformation of the fifth relative position.

According to the solution provided in the manner 4, the configurationinformation of the bandwidth part may be carried in remaining minimumsystem information (RMSI) other than a MIB. Therefore, indicationsignaling overheads of the MIB are reduced. In addition, the RMSI maycarry more bit information, and further, an offset of a bandwidth partin frequency domain may be more flexible, that is, an offset granularityin frequency domain may be smaller. Therefore, the offset of thebandwidth part is more flexible, and resource utilization can beimproved.

For example, the network device sends higher layer signaling to theterminal device, where the higher layer signaling includes configurationinformation of a system bandwidth, and the higher layer signalingincludes at least one of RRC signaling, system information, RMSI, or thelike.

An offset of a center frequency of the bandwidth part relative to acenter frequency may include at least one of the following:

For example, the higher layer signaling may explicitly indicate, thatthe fifth relative position may be at least one value in a value set. Asshown in FIG. 9, the value set may be predefined. For example, the valueset may be {−2N^(Offset_BP) _(RB), −N^(Offset_BP) _(RB), 0,+N^(Offset_BP) _(RB), +2N^(Offset_BP) _(RB)}. As shown in FIG. 9, afifth relative position 1 of a bandwidth 0 is −2N^(Offset_BP) _(RB); afifth relative position 2 of a bandwidth 1 is −N^(Offset_BP) _(RB); afifth relative position 4 of a bandwidth 2 is 0; a fifth relativeposition 3 of a bandwidth 3 is +N^(Offset_BP) _(RB); and a fifthrelative position 2 of a bandwidth 5 is +2N^(Offset_BP) _(RB).

It should be especially noted that, at least one value in the predefinedvalue set corresponds to the control channel resource set included in asystem bandwidth. The predefined value set may be predefined, or may bespecified by a protocol, or may be preconfigured. This is notspecifically limited in this application.

For another example, the higher layer signaling sent by the networkdevice to the terminal device includes the bandwidth configurationinformation including a quantity of bandwidths, where a size of afrequency domain resource occupied by each subband is equal. The higherlayer signaling includes system information, RMSI (Remaining minimumsystem information), RRC signaling, or the like.

For another example, as shown in Table 4, the terminal device maydetermine the fifth relative position information based on the quantityof bandwidths and a number of a bandwidth subset.

TABLE 4 Indication Fifth relative Bandwidth information position 0 0−N^(CORESET) ^(—) ^(offset) _(RB)/4 1 1 +N^(CORESET) ^(—) ^(offset)_(RB)/4

As shown in FIG. 10, the system carrier bandwidth includes two subsets:a bandwidth 0 and a bandwidth 1, configured by using the higher layersignaling. A maximum quantity of physical resource blocks included in adownlink system carrier bandwidth in frequency domain is N^(max) _(DL),or a quantity of physical resource blocks within a bandwidth included ina downlink system carrier bandwidth is N^(max_BP) _(DL), where a valueof N^(max_BP) _(DL) or N^(max) _(DL) is a value predefined by thesystem. A value of the fifth relative position may be determined basedon the quantity of included bandwidths. For example, if the quantity ofbandwidths is 2, the fifth relative position is {−N^(max) _(DL)/4,+N^(max) _(DL)/4}. In this case, it indicates that the fifth relativeposition corresponding to the bandwidth 0 of the control channelresource set is −N^(max) _(DL)/4, or +N^(max) _(DL)/4.

As shown in FIG. 11, the system carrier bandwidth includes threebandwidths: a bandwidth 0, a bandwidth 1, and a bandwidth 2, configuredby using the higher layer signaling, as shown in Table 5.

TABLE 5 Indication Fifth relative Bandwidth information position 0 0−N^(max) _(DL)/3 1 1 0 2 2 +N^(max) _(DL)/3

A maximum quantity of physical resource blocks included in a downlinksystem carrier bandwidth in frequency domain is N^(max) _(DL). In thiscase, it may be determined, based on the quantity of includedbandwidths, that a value of the fifth relative position is {−N^(max)_(DL)/3, 0, +N^(max) _(FL)/3}. If it is indicated that the controlchannel resource set is within the bandwidth 0, a fifth relativeposition 0 is −N^(max) _(DL)/3, but a fifth relative position 1 is 0,and a fifth relative position 2 is +N^(max) _(DL)/3.

For example, the correspondence between the bandwidth, the indicationinformation, and the fifth relative position may be predefined by thenetwork device and the terminal device, or may be specified by aprotocol, or may be preconfigured. This is not specifically limited inthis application, and shall fall within the protection scope of thisapplication as long as the correspondence between the bandwidth, theindication information, and the fifth relative position can bereflected.

For example, the bandwidth configuration method further includes amethod similar to a resource allocation type 2 Type2 in the LTE network.Details are not described herein.

For example, the control channel resource set is within the bandwidth.Position information of the control channel resource set relative to acenter or boundary of the bandwidth is determined by the configurationinformation included in the higher layer signaling, and the higher layersignaling includes RRC signaling or RAR signaling, or the like.

For example, a position of the bandwidth comprising the control channelresource set may be marked as an offset position 0, as shown in Table 6.

TABLE 6 Control channel Indication resource set information Offsetposition 0 0 000 −2N^(CORESET) ^(—) ^(offset) _(RB) 1 001  −N^(CORESET)^(—) ^(offset) _(RB) 2 010 0 3 011  +N^(CORESET) ^(—) ^(offset) _(RB) 4100 +2N^(CORESET) ^(—) ^(offset) _(RB)

As shown in FIG. 12, the terminal device determines the offset positionaccording to the fifth relative position and the offset position 0.

For example, the control channel resource set is within the bandwidth.The offset position 0 of the control channel resource set relative tothe center or boundary of the bandwidth is determined by theconfiguration information included in the higher layer signaling, andthe higher layer signaling includes RRC signaling or RAR signaling, orthe like.

For a manner of obtaining the first sequence by the terminal devicebased on the position offset information, refer to a manner of obtainingthe first sequence based on the position offset information in themanner 1. Details are not described again herein.

For example, the correspondence between the control channel resourceset, the indication information, and the offset position 0 may bepredefined by the network device and the terminal device, or may bespecified by a protocol, or may be preconfigured. This is notspecifically limited in this application, and shall fall within theprotection scope of this application as long as the correspondencebetween the control channel resource set, the indication information,and the offset position 0 can be reflected.

Manner 5: The terminal device receives configuration information of abandwidth, where the configuration information includes indicationinformation of a sixth relative position and indication information of aseventh relative position, the sixth relative position is a relativeposition of a bandwidth comprising the control channel resource setrelative to a reference point of a broadcast channel carrying a MIB, andthe seventh relative position is a position of the reference point ofthe broadcast channel carrying the MIB, relative to a frequency domainreference point; and that a terminal device obtains position offsetinformation includes: determining the position offset informationaccording to the sixth relative position indicated by the indicationinformation of the sixth relative position and the seventh relativeposition indicated by the indication information of the seventh relativeposition.

It should be especially emphasized that the position offset informationmay be obtained according to the sixth relative position and the seventhrelative position by using any one of the following methods: forexample, performing one or more of summation, deduction, multiplication,or division processing on the sixth relative position and the seventhrelative position to determine the position offset information.

According to the solution provided in the manner 5, the configurationinformation of the bandwidth may be carried in RMSI other than a MIB.Therefore, indication signaling overheads of the MIB are reduced. Inaddition, the RMSI may carry more bit information, and further, anoffset of the bandwidth in frequency domain may be more flexible, thatis, an offset granularity in frequency domain may be smaller. Therefore,the offset of the bandwidth is more flexible, and resource utilizationcan be improved.

An implementation of the sixth relative position in the manner 5 may be:predefining a value set {−2N^(Offset_BP) _(RB), −N^(Offset_BP) _(RB), 0,+^(Offset_PR) _(RB), +2N^(Offset_BP) _(RB)} of the sixth relativeposition, and configuring a value of the sixth relative positioncorresponding to the bandwidth.

An implementation of the seventh relative position in the manner 5 maybe: as shown in Table 7, indication information corresponding to areference point 0 of a broadcast channel is 000, and a seventh relativeposition 1 is 0; indication information corresponding to a referencepoint 2 of a broadcast channel is 001, and a seventh relative position 2is +N^(Offset) _(RB).

TABLE 7 Reference point of a Indication Seventh relative broadcastchannel information position 0 000 0 2 001  +N^(Offset) _(RB) 4 010+2N^(Offset) _(RB) 1 011  −N^(Offset) _(RB) 3 100 −2N^(Offset) _(RB)

A value of the seventh relative position in Table 7 indicates an offsetof a quantity of units of physical resource blocks, of the referencepoint of the broadcast channel relative to the frequency domainreference point. It is noted that in this embodiment, only the quantityof offset physical resource blocks is used as an example for indicatinga value of the predefined offset. An actually predefined offset may bepredefined as other resource units, and is not limited herein.

As shown in FIG. 13, indication information of a reference point 1 of abroadcast channel is {011}, and a seventh relative position 2 is{−N^(Offset) _(RB)}; indication information of a reference point 2 of abroadcast channel is {001}, and a seventh relative position 4 is{+N^(Offset) _(RB)}; indication information corresponding to a referencepoint 3 of a broadcast channel is {100}, and a seventh relative position1 is {−2N^(Offset) _(RB)}; indication information corresponding to areference point 4 of a broadcast channel is {010}, and a seventhrelative position 5 is {+2N^(Offset) _(RB)}; indication informationcorresponding to a reference point 0 of a broadcast channel is {000},and a seventh relative position 3 is {0}.

FIG. 14 is a schematic diagram of a correspondence between a sixthrelative position and a seventh relative position. As shown in FIG. 14,a sixth relative position 0 is −N^(Offset_BP) _(RB), but a seventhrelative position 5 is +2N^(Offset_BP) _(RB). In this case, the offsetposition is (−N^(Offset_BP) _(RB)+2N^(Offset_BP) _(RB)).

For a manner of obtaining the first sequence by the terminal devicebased on the position offset information, refer to a manner of obtainingthe first sequence based on the position offset information in themanner 1. Details are not described again herein.

For example, the correspondence between the reference point of thebroadcast channel, the indication information, and the seventh relativeposition may be predefined by the network device and the terminaldevice, or may be specified by a protocol, or may be preconfigured. Thisis not specifically limited in this application, and shall fall withinthe protection scope of this application as long as the correspondencebetween the reference point of the broadcast channel, the indicationinformation, and the seventh relative position can be reflected.

Manner 6: the terminal device receives configuration information of thecontrol channel resource set, where the configuration information of thecontrol channel resource set includes indication information used toindicate the position offset information.

According to the solution provided in the manner 6, when configuringtime-frequency resources of the control channel resource set, a networkdevice obtains an overlapping resource region on the time-frequencyresources, and determines the position offset information according tothe overlapping resource region, and when configuring the controlchannel resource set, configures position offset information of a firstsequence used by a control channel reference signal, so that referencesignal sequences of a plurality of control channels are the same in theoverlapping region. Therefore, orthogonal reuse by a plurality of users,that is, orthogonal MU-MIMO, is enabled. In addition, non-orthogonalinterference between sequences that is caused by a plurality ofdifferent sequences on a same reference signal resource can be reduced.

For example, the indication information used to indicate the positionoffset information includes indication information used to indicate aphysical resource block number of the control channel resource set andthe method further includes: the terminal device determines the positionoffset information according to a physical resource block indicated bythe physical resource block number. According to this solution, allcontrol channel resources use a same physical resource block number, anda reference point of the physical resource block number may be notifiedby a MIB or RMSI, and further, the terminal device obtains the unifiedphysical resource block number in frequency domain according to a samefrequency domain reference point. Therefore, first sequences determinedfor control channel resource sets including the same physical resourceblock number are the same, so that first sequences of control channelresource sets with overlapping resources are the same. Therefore,orthogonal reuse by a plurality of users, that is, orthogonal MU-MIMO,is enabled.

For example, the indication information of the physical resource blocknumber may be a unified physical resource block number that existswithin a whole system bandwidth. As shown in FIG. 15, because the centerfrequency is located in a resource block numbered 0, if physicalresource block numbers corresponding to the control channel resource setare {n^(CORESET), n^(CORESET), . . . , N^(CORESET) _(RB)-1}, whereN^(CORESET) _(RB) is a total quantity of physical resource blocksincluded in the control channel resource set, the position offsetinformation may be determined by using n^(CORESET). As shown in FIG. 16,N^(CORESET) _(RB)=5, and n^(CORESET)=2. In this case, a set of physicalresource block numbers included in the control channel resource set is{2, 3, 4, 5, 6}, and the position offset information is 2.

It should be especially emphasized that using the quantity of physicalresource blocks as an offset is merely an example in this embodiment ofthis application. This application includes but is not limited to this.Use of other equivalents shall fall within the protection scope of thisapplication as long as the offset relative to the center frequency canbe obtained.

If the frequency domain reference point is a boundary of a systemcarrier bandwidth, the physical resource block number of the frequencydomain reference point is 0, and the offset position is n^(CORESET).

For a manner of obtaining the first sequence by the terminal devicebased on the position offset information, refer to a manner of obtainingthe first sequence based on the position offset information in themanner 1. Details are not described again herein.

In another example, the method for obtaining the first sequence based onthe offset position further includes generating the first sequence basedon the offset position.

In a possible implementation method, the obtained offset position isn_(offset), and the first sequence may be generated by using a formula(2):

$\begin{matrix}{{{r(m)} = {{\frac{1}{\sqrt{2}}\left( {1 - {2 \cdot {c\left( {2m} \right)}}} \right)} + {j\frac{1}{\sqrt{2}}\left( {1 - {2 \cdot {c\left( {{2m} + 1} \right)}}} \right)}}},{m = 0},1,\ldots\;,{{n_{RE}^{RB} \cdot N_{RB}^{CORESET}} - 1}} & (2)\end{matrix}$

In the formula (2), N^(CORESET) _(RB) corresponds to a quantity ofphysical resource blocks occupied by the control channel resource set,where a quantity of resource elements included in each physical resourceblock and used for mapping a reference channel is n^(RB) _(RE); and c(n)may be obtained by using a formula (3):

c(n)=(x ₁(n+N _(C))+x ₂(n+N _(C)))mod 2

x ₁(n+31)=(x ₁(n+3)+x ₁(n))mod 2

x ₂(n+31)=(x ₂(n+3)+x ₂(n+2)+x ₂(n+1)+x ₂(n))mod 2   (3)

In the formula (3), N_(C)=1600+n_(offset).

The foregoing method is applicable not only to a control channelresource set including a single symbol but also to a control channelresource set of a plurality of symbols. Details are not describedherein.

This embodiment ensures that when a plurality of control channelresource sets overlap each other on time-frequency resources, orthogonalcode division multiplexing can be implemented for reference signalsmapped on the overlapping time-frequency resources.

In another example, the terminal device generates a reference signalsequence. Step 205 in which the terminal device obtains a first sequencebased on the offset position includes: the terminal device obtains thefirst sequence from the reference signal sequence based on the positionoffset information, where the first sequence is a subset of thereference signal sequence, and the offset position is a position of atleast one value of the first sequence in the reference signal sequence.

example, the reference signal sequence is a pseudo random aperiodicsequence, and the reference signal sequence may be generated accordingto a formula (4):

$\begin{matrix}{{{r(m)} = {{\frac{1}{\sqrt{2}}\left( {1 - {2 \cdot {c\left( {2m} \right)}}} \right)} + {j\frac{1}{\sqrt{2}}\left( {1 - {2 \cdot {c\left( {{2m} + 1} \right)}}} \right)}}},{m = 0},1,\ldots\;,{{4N_{RB}^{\max,{DL}}} - 1}} & (4)\end{matrix}$

where N_(RB) ^(max,DL) is a maximum quantity of a physical resourceblocks included in the system bandwidth. In this embodiment, the controlchannel resource set occupies one OFDM symbol in time domain, and eachREG in the control channel resource set includes four resource elementsused for mapping reference signals.

Part 205: The terminal device obtains a first sequence based on theposition offset information.

Part 206: The terminal device demodulates, by using the first sequence,a control channel signal carried in the control channel resource set, toobtain downlink control information.

In an example, the terminal device may obtain the downlink controlinformation in the following manner:

The terminal device detects a control channel in the control channelresource set, performs related processing on a received control channelreference signal by using the first sequence, estimates channel stateinformation of a time-frequency resource on which the control channel islocated, and demodulates and decodes the received control channel signalaccording to the channel state information to obtain the downlinkcontrol information.

It should be especially noted that, part 201 to part 203 in theembodiment shown in FIG. 2 may be used as an embodiment. Part 204 topart 206 may be used as another embodiment separately. In addition, asequence of performing part 201 to part 206 in the embodiment shown inFIG. 2 may also be another sequence. This is not specifically limited inthis application.

For example, on a basis of the foregoing manner 4, manner 5, and manner6, the method may further include part 207: The terminal device receivesa master information block MIB sent by the network device, where the MIBincludes indication information used to indicate an eleventh relativeposition of the control channel resource set relative to a referencepoint of a broadcast channel carrying the MIB; and the terminal deviceobtains the second sequence from the reference signal sequence accordingto the eleventh relative position, where the second sequence is a subsetof the reference signal sequence, and the eighth relative position is aposition of at least one value of the second sequence in the referencesignal sequence.

It should be especially noted that, part 207 may be used in combinationwith part 204 to part 206 in the embodiment shown in FIG. 2. This is notspecifically limited in this application. A specific execution sequencemay be determined flexibly. For example, part 207 may be performed firstor may be performed before one of part 204 to part 206.

In the method, the MIB does not need to carry indication information ofthe frequency domain reference point. Therefore, indication signalingoverheads of the MIB are reduced. In addition, the frequency domainreference point is indicated by RMSI occupying more resources.Therefore, bandwidth configurations are more flexible, fragments of thebandwidth in use are reduced, and spectrum utilization is improved.

The second sequence is used for a reference signal included in a firstcontrol channel resource set configured by the MIB, and the firstcontrol channel resource set includes a common search space, and mainlycarries control information for scheduling the RMSI. The foregoing firstsequence is used for the control channel resource set configured by RRC,and the first control channel resource set includes a common searchspace and/or a user specific search space, and mainly carries controlinformation for scheduling data.

FIG. 17 is a schematic flowchart of another method for obtaining areference signal sequence according to an embodiment of thisapplication. The method includes the following parts.

Part 301: A network device obtains an initial value for generating afirst sequence or length information of a first sequence.

Part 302: The network device generates the first sequence based on theinitial value or the length information of the first sequence.

Part 303: The network device maps the first sequence to a resourceelement carrying a reference signal in a control channel resource set.

In an example, the network device sends a MIB to a terminal device,where the MIB includes indication information used to indicate atime-frequency resource occupied by the control channel resource set.

In an example, the network device sends one or more of a synchronizationsignal, a broadcast channel scrambling sequence, a broadcast channelreference signal, or broadcast information that includes the initialvalue for generating the first sequence to the terminal device.

It should be especially noted that, for how details about step 303 inwhich the network device maps the first sequence to the resource elementcarrying the reference signal in the control channel resource set,reference may be made to the embodiment shown in FIG. 2.

According to the solution shown in FIG. 17, the MIB does not includeindication information of a frequency domain reference point, andtherefore, indication signaling overheads of the MIB can be reduced.Therefore, the terminal device cannot obtain a position relative to thefrequency domain reference, and can only directly generate a referencesignal sequence, or truncate the first sequence from a center positionof a reference signal sequence. Because a size of an initial accessbandwidth is limited, it is less possible that control channel resourcesets sent in different frequency bands in frequency domain overlap eachother in frequency domain. Therefore, reuse by a plurality of users isimpossible. However, a terminal device receiving RMSI can obtain thefirst sequence according to a reference point configured by the RMSI,and orthogonal reuse by a plurality of users, that is, MU-MIMO, can beimplemented in an overlapping resource region between a plurality ofcontrol channel resource sets.

FIG. 18 is another method for obtaining a reference signal sequenceaccording to an embodiment of this application. The method includes thefollowing parts.

Part 401: A terminal device obtains an initial value for generating afirst sequence or length information of a sequence.

Part 402: The terminal device generates the first sequence based on theinitial value or the length information of the first sequence.

Part 403: The terminal device demodulates, by using the first sequence,a control channel signal carried in a control channel resource set, toobtain downlink control information.

In an example, the method further includes: the terminal device receivesa MIB, where the MIB includes indication information used to indicate atime-frequency resource occupied by the control channel resource set;and that a terminal device obtains length information of a firstsequence includes: determining a length of the first sequence accordingto the indication information used to the time-frequency resourceoccupied by the control channel resource set.

In an example, that a terminal device obtains an initial value forgenerating a first sequence includes: the terminal device obtains one ormore of a synchronization signal, a broadcast channel scramblingsequence, a broadcast channel reference signal, or broadcast informationthat includes the initial value for generating the first sequence.

It should be noted that, the embodiment shown in FIG. 17 may be used incombination with the embodiment shown in FIG. 18. A sequence of steps inthe combined process may comply with sequences of steps in FIG. 17 andFIG. 18, or may not comply with sequences of steps in FIG. 17 and FIG.18. This is not limited.

It should be especially noted that, for how the terminal demodulates, byusing the first sequence, the control channel signal carried in thecontrol channel resource set, to obtain the downlink controlinformation, reference may be made to the embodiment shown in FIG. 2.Details are not described again herein.

In an example, that a terminal device obtains length information of thefirst sequence in step 401 may include: the terminal device generatesthe first sequence, where a length of the first sequence is indicated bya MIB.

In another example, the terminal device may generate the initial valueof the first sequence by using one or more configurations of asynchronization signal, a broadcast channel scrambling sequence, abroadcast channel reference signal, or broadcast information. Thisensures randomicity of a reference signal sequence used in the controlchannel resource set, and can avoid interference caused by another cellto a reference signal in the control channel resource set.

For example, the initial value of the first sequence may be determinedby using a formula (5):

c _(init)=(n _(s)+1)·(2n _(ID) ^(CSS)+1)·2¹⁶ +n _(ID)   (5)

where n_(ID) is configured by indication information carried in the MIB,but n^(CSS) _(ID) is a predefined value; or n^(CSS) _(ID) may beconfigured by indication information carried in broadcast information,but n_(ID) is a predefined value.

For example, the MIB includes the information used to indicate thetime-frequency resource occupied by the control channel resource set,and/or configuration information of a reference signal resource includedin the control channel resource set.

For example, the terminal device may determine the length of the firstsequence according to a size of the time-frequency resource, occupied bythe control channel resource set and included in the MIB.

For example, a quantity of physical resource blocks included in thecontrol channel resource set in frequency domain and configured by theMIB is N^(CORESET) _(RB), a quantity of OFDM symbols included in timedomain is M^(CORESET) _(os), and the system specifies in advance that aquantity of resources occupied by a reference signal included in eachREG is N^(REG) _(RS). In this case, the length of the first sequence isN^(REG) _(RS)·N^(CORESET) _(RB)·M^(CORESET) _(os).

For another example, as shown in Table 8, the configuration informationindicates that a quantity of resource elements included in the REG andused for mapping the reference signal is 3; and it is determined, basedon the quantity N^(CORESET) _(RB) of physical resource blocks includedin the control channel resource set in frequency domain and the quantityM^(CORESET) _(os) of OFDM symbols included in time domain, that thelength of the first sequence is 3·N^(CORESET) _(RB)·M^(CORESET) _(os).

TABLE 8 Indication Quantity of REs of a reference information signal(N^(REG) _(RS)) 00 3 01 2 11 4

According to this solution, the MIB does not include indicationinformation of a frequency domain reference point, and therefore,indication signaling overheads of the MIB can be reduced. Therefore, theterminal device cannot obtain a position relative to the frequencydomain reference, and can only directly generate a reference signalsequence, or truncate the first sequence from a center position of areference signal sequence. Because a size of an initial access bandwidthis limited, it is less possible that control channel resource sets sentin different frequency bands in frequency domain overlap each other infrequency domain. Therefore, reuse by a plurality of users isimpossible. However, a terminal device receiving RMSI can obtain thefirst sequence according to a reference point configured by the RMSI,and orthogonal reuse by a plurality of users, that is, MU-MIMO, can beimplemented in an overlapping resource region between a plurality ofcontrol channel resource sets.

For example, the correspondence between the indication information andthe quantity of REs of the reference signal may be predefined by anetwork device and the terminal device, or may be specified by aprotocol, or may be preconfigured. This is not specifically limited inthis application, and shall fall within the protection scope of thisapplication as long as the correspondence between the indicationinformation in the broadcast channel and the quantity of REs of thereference signal can be reflected.

FIG. 19 is another method for obtaining a reference signal according toan embodiment of this application. The method includes the followingparts.

Part 501: A terminal device generates a broadcast channel referencesignal sequence.

For example, the terminal device may generate the broadcast channelreference signal sequence by using a formula (6):

$\begin{matrix}{{{r(m)} = {{\frac{1}{\sqrt{2}}\left( {1 - {2 \cdot {c\left( {2m} \right)}}} \right)} + {j\frac{1}{\sqrt{2}}\left( {1 - {2 \cdot {c\left( {{2m} + 1} \right)}}} \right)}}},{m = 0},1,\ldots\;,{{8N_{RB}^{\max,{DL}}} - 1}} & (6)\end{matrix}$

where N^(max,DL) _(RB) indicates a maximum quantity of a physicalresource blocks included in a system bandwidth; because a quantity ofOFDM symbols occupied by a broadcast channel is 2 (which may beconsecutive or discrete), the reference signal sequence is mapped to afirst OFDM symbol and a second OFDM symbol in ascending order offrequencies, as shown in FIG. 20.

It should be especially noted that, a time-frequency resource positionof a broadcast channel reference signal is merely an example forunderstanding this embodiment of this application. This applicationincludes but is not limited to this. In other words, other manners maybe used in 5G to describe a resource position to which a broadcastchannel reference signal is mapped.

Part 502: A network device sends a broadcast channel reference signal tothe terminal device, where the broadcast channel reference signalincludes a subset of the broadcast channel reference signal sequence.

For example, a correspondence between the subset of the reference signalsequence and a ninth relative position is predefined, as shown in Table9. The broadcast reference signal sequence is determined according to acorrespondence between subsets of different reference signal sequencesand different relative positions.

TABLE 9 Subset of a reference signal sequence Ninth relative position 0−2N^(Offset) _(RB) 1  −N^(Offset) _(RB) 2 0 3  +N^(Offset) _(RB) 4+2N^(Offset) _(RB)

For example, FIG. 20 provides a sequence truncated from a broadcastchannel reference signal sequence included in a broadcast channel 2,where numbers of elements in a reference signal sequence number includedin a broadcast channel reference signal on a first OFDM symbol are{2N^(max,DL) _(RB)−2N^(PBCH) _(RB)+N^(Offset) _(RB), . . . , 2N^(max,DL)_(RB)+2N^(PBCH) _(RB)+N^(Offset) _(RB)−1}; and numbers of elements in areference signal sequence included on a second OFDM symbol is{6N^(max,DL) _(RB)−2N^(PBCH) _(RB)+N^(Offset) _(RB), . . . , 6N^(max,DL)_(RB)+2N^(PBCH) _(RB)+N^(Offset) _(RB)−1}.

For example, the correspondence between the subset of the referencesignal sequence and the ninth relative position may be predefined by thenetwork device and the terminal device, or may be specified by aprotocol, or may be preconfigured. This is not specifically limited inthis application, and shall fall within the protection scope of thisapplication as long as the correspondence between the subset of thebroadcast channel reference signal sequence and the ninth relativeposition can be reflected.

For example, a frequency domain reference point may be a minimumfrequency within a system bandwidth in frequency domain, or a maximumfrequency within a system bandwidth in frequency domain. Details are notdescribed herein.

For example, the terminal device determines, by blindly detecting thereference signal sequence, a frequency domain position of the receivedbroadcast channel, or determines frequency domain offset information ofthe broadcast channel relative to a reference position of the systembandwidth in frequency domain.

Part 503: The terminal device receives the broadcast channel referencesignal sent by the network device, where the broadcast channel referencesignal includes the subset of the broadcast channel reference signalsequence.

Part 504: The network device sends a MIB to the terminal device, wherethe MIB includes indication information used to indicate a tenthrelative position of the control channel resource set relative to abroadcast channel.

Part 505: The terminal device receives the MIB.

Part 506: The terminal device obtains position offset information basedon a ninth relative position corresponding to the subset of thebroadcast channel reference signal sequence and the tenth relativeposition indicated by the indication information of the tenth relativeposition.

Part 507: The terminal device obtains a first sequence based on theposition offset information.

For example, the first sequence is a subset of a control channelreference signal sequence.

For example, the control channel reference signal sequence is a pseudorandom aperiodic sequence, and may be obtained according to a formula(7):

$\begin{matrix}{{{r(m)} = {{\frac{1}{\sqrt{2}}\left( {1 - {2 \cdot {c\left( {2m} \right)}}} \right)} + {j\frac{1}{\sqrt{2}}\left( {1 - {2 \cdot {c\left( {{2m} + 1} \right)}}} \right)}}},{m = 0},1,\ldots\;,{{4N_{RB}^{\max,{DL}}} - 1}} & (7)\end{matrix}$

where N_(RB) ^(max,DL) is a maximum quantity of a physical resourceblocks included in the system bandwidth. In this embodiment, the controlchannel resource set occupies one OFDM symbol in time domain, and eachREG in the control channel resource set includes four resource elementsused for mapping reference signals. The REG includes resource elementsof control information and resource elements carrying the referencesignal.

For another example, the control channel reference signal sequence is apseudo periodic sequence, and may be obtained according to a formula(8):

$\begin{matrix}{{{r(m)} = {{\frac{1}{\sqrt{2}}\left( {1 - {2 \cdot {c\left( {2m} \right)}}} \right)} + {j\frac{1}{\sqrt{2}}\left( {1 - {2 \cdot {c\left( {{2m} + 1} \right)}}} \right)}}},{m = 0},1,\ldots\;,{{4N_{RB}^{{Ref}.}} - 1}} & (8)\end{matrix}$

A length of the control channel reference signal sequence includes onlyN^(Ref) _(RB), where N^(Ref) _(RB) indicates a quantity of resourceblocks, and N^(Ref) _(RB)<N^(max,DL) _(RB), where N^(max,DL) _(RB) is amaximum quantity of a physical resource blocks included in the systembandwidth. However, the control channel reference signal sequence may bemapped to a whole carrier in a repetition manner, as shown in FIG. 21.

Part 508: The terminal device demodulates and decodes the controlchannel, by using the first sequence, a control channel carried in thecontrol channel resource set, to obtain control information.

For a specific method for demodulating and decoding the control channel,and obtaining the control information, refer to a method fordemodulating and decoding the control channel, and obtaining controlinformation in the LTE network. Details are not excessively described inthis application.

The foregoing describes the solutions provided by the embodiments ofthis application from a perspective of interaction between networkelements. It may be understood that, to implement the foregoingfunctions, each network element, for example, UE, a base station, or acore network entity, includes a corresponding hardware structure and/ora software module for performing each function. A person of ordinaryskill in the art should easily be aware that, in combination with theexamples described in the embodiments disclosed in this specification,units, algorithms steps may be implemented by hardware or a combinationof hardware and computer software. Whether a function is performed byhardware or hardware driven by computer software depends on particularapplications and design constraints of the technical solutions. A personskilled in the art may use different methods to implement the describedfunctions for each particular application, but it should not beconsidered that the implementation goes beyond the scope of thisapplication.

An embodiment of this application provides a terminal device. Theapparatus including:

a processor 60l, configured to control actions of the terminal device,and perform processing performed by the terminal device in theembodiment shown in FIG. 2, for example, configured to obtain positionoffset information, obtain a first sequence based on the position offsetinformation, and demodulate, by using the first sequence, a controlchannel signal carried in a control channel resource set, to obtaindownlink control information.

For example, the processor is further configured to generate a referencesignal sequence; and the processor is specifically configured to obtainthe first sequence from the reference signal sequence based on theposition offset information, where the first sequence is a subset of thereference signal sequence, and the position offset information is aposition of at least one value of the first sequence in the referencesignal sequence.

For example, as shown in FIG. 22, the terminal device further includes areceiver 602, configured to receive a master information block MIB sentby a network device, where the MIB includes indication information usedto indicate a first relative position and indication information used toindicate a second relative position, the first relative position is aposition of a reference point of a broadcast channel carrying the MIB,relative to a frequency domain reference point, and the second relativeposition is a relative position of the control channel resource setrelative to the reference point of the broadcast channel; and theprocessor is specifically configured to determine the position offsetinformation according to the first relative position indicated by theindication information of the first relative position and the secondrelative position indicated by the indication information of the secondrelative position that are received by the receiving module 602.

For example, the terminal device further includes a receiver 602,configured to receive a MIB sent by a network device, where the MIBincludes indication information used to indicate a third relativeposition, and the third relative position is a position of a referencepoint of a broadcast channel carrying the MIB, relative to a frequencydomain reference point; and

the processor is specifically configured to determine the positionoffset information according to the third relative position indicated bythe indication information of the third relative position that isreceived by the receiver and a fourth relative position, where thefourth relative position is a relative position of the control channelresource set relative to the reference point of the broadcast channel,and the fourth relative position is configured or preset.

For example, the processor is further configured to instruct theprocessor 602 to receive a MIB sent by a network device, where the MIBincludes indication information used to indicate eighth relativeposition information of the control channel resource set relative to afrequency domain reference point; and the processor is specificallyconfigured to determine the position offset information according to theeighth relative position indicated by the indication information of theeighth relative position.

For example, the terminal device further includes a receiver 602,configured to receive configuration information of the bandwidth subsetincludes indication information of a fifth relative position, and thefifth relative position is a relative position of a system bandwidthsubset of the control channel resource set relative to a frequencydomain reference point; and

the processor is specifically configured to determine the positionoffset information according to the fifth relative position indicated bythe indication information of the fifth relative position that isreceived by the receiver.

For example, the terminal device further includes a receiver 602,configured to receive configuration information of a system bandwidthsubset, where the configuration information of the subset includesindication information of a sixth relative position and indicationinformation of a seventh relative position, the sixth relative positionis a relative position of a system bandwidth subset of the controlchannel resource set relative to a reference point of a broadcastchannel carrying a MIB, and the seventh relative position is a positionof the reference point of the broadcast channel carrying the MIB,relative to a frequency domain reference point; and

the processor is specifically configured to determine the positionoffset information according to the sixth relative position indicated bythe indication information of the sixth relative position and theseventh relative position indicated by the indication information of theseventh relative position that are received by the receiver.

For example, the processor is further configured to instruct a receiverto receive configuration information of the control channel resourceset, where the configuration information of the control channel resourceset includes indication information used to indicate the position offsetinformation.

For example, the processor is specifically configured to: when theindication information used to indicate the position offset informationincludes indication information used to indicate a physical resourceblock number of the control channel resource set, determine the positionoffset information according to a physical resource block indicated bythe physical resource block number.

For example, the configuration information of the control channelresource set includes at least one of a random access response RAR andradio resource control RRC signaling, and the control channel resourceset includes a type-1 common search space CSS and/or a terminal specificsearch space USS.

The terminal device further includes a receiver 602, configured toreceive a master information block MIB sent by a network device, wherethe MIB includes indication information used to indicate an eleventhrelative position of the control channel resource set relative to areference point of a broadcast channel carrying the MIB; and

the processor 601 is specifically configured to obtain a second sequencefrom the reference signal sequence according to the eleventh relativeposition, where the second sequence is a subset of the reference signalsequence, and the eighth relative position is a position of at least onevalue of the second sequence in the reference signal sequence.

For example, the terminal device may further include a memory 603,configured to store program code and data of the terminal device.

For example, the terminal device may further include a transmitter 604and a modem processor 605. The transmitter 604 is configured to adjust(for example, perform analog conversion, filtering, amplification, andup-conversion) an output sample and generate an uplink signal, where theuplink signal is transmitted to the network device in the foregoingembodiment by using an antenna. On a downlink, the antenna receives adownlink signal transmitted by the network device in the foregoingembodiment. The receiver 602 adjusts (for example, performs filtering,amplification, down-conversion, and digitization) the signal receivedfrom the antenna and provides an input sample. In the modem processor605, an encoder receives service data and a signaling message to be senton an uplink, and performs processing (for example, format conversion,encoding, and interleaving) on the service data and signaling message. Amodulator further processes (for example, performs symbol mapping andmodulation) the encoded service data and signaling message and providesan output sample. A demodulator processes (for example, demodulates) theinput sample and provides a symbol estimation. A decoder processes (forexample, de-interleaves and decodes) the symbol estimation and providesdata and a signaling message that are decoded and sent to the terminaldevice. The encoder, the modulator, the demodulator, and the decoder maybe implemented by a composite modem processor 605. The units performprocessing based on a radio access technology (for example, accesstechnology of LTE system or another evolved systems) used by a radioaccess network.

It should be especially noted that, for beneficial effects of thisembodiment, reference may be made to the method embodiment shown in FIG.2. Details are not described again herein.

An embodiment of this application further provides a network device,including:

a processor 701, configured to control actions of the network device,and perform processing performed by the network device in the embodimentshown in FIG. 2. For example, the processor is configured to obtainposition offset information, obtain a first sequence based on theposition offset information, and map the first sequence to a resourceelement carrying a reference signal in a control channel resource set.

For example, the processor is configured to generate a reference signalsequence, and obtain the first sequence from the reference signalsequence based on the position offset information, where the firstsequence is a subset of the reference signal sequence, and the positionoffset information is a position of at least one value of the firstsequence in the reference signal sequence.

For example, as shown in FIG. 23, the network device further includes atransmitter 702, configured to send a MIB to a terminal device, wherethe MIB includes indication information of a first relative position andindication information of a second relative position, the first relativeposition is a position of a reference point of a broadcast channelcarrying the MIB, relative to a frequency domain reference point, thesecond relative position is a relative position of the control channelresource set relative to the reference point of the broadcast channel,and the indication information of the first relative position and theindication information of the second relative position are used toindicate the position offset information.

For example, the network device further includes a transmitter 702,configured to send a MIB to a terminal device, where the MIB includesindication information of a third relative position, the third relativeposition is a position of a reference point of a broadcast channelcarrying the MIB, relative to a frequency domain reference point, theindication information of the third relative position is used with afourth relative position to indicate the position offset information,the fourth relative position is a relative position of the controlchannel resource set relative to the reference point of the broadcastchannel, and the fourth relative position is configured or preset.

For example, the network device further includes a transmitter 702,configured to send a master information block MIB to a terminal device,where the MIB includes indication information used to indicate eighthrelative position information of the control channel resource setrelative to a frequency domain reference point, and the indicationinformation of the eighth relative position information is used toindicate the position offset information.

For example, the network device further includes a transmitter 702,configured to send configuration information of a system bandwidthsubset to a terminal device, where the configuration information of thesubset includes indication information of a fifth relative position, thefifth relative position is a relative position of a system bandwidthsubset of the control channel resource set relative to a frequencydomain reference point, and the indication information of the fifthrelative position is used to indicate the position offset information.

For example, the network device further includes a transmitter 702,configured to send configuration information of a system bandwidthsubset to a terminal device, where the configuration information of thesubset includes indication information of a sixth relative position andindication information of a seventh relative position, the sixthrelative position is a relative position of a system bandwidth subset ofthe control channel resource set relative to a reference point frequencydomain position of a broadcast channel carrying a MIB, the seventhrelative position is a position of the reference point of the broadcastchannel carrying the MIB, relative to a frequency domain referencepoint, and the indication information of the sixth relative position andthe indication information of the seventh relative position are used toindicate the position offset information.

For example, the network device further includes a transmitter 702,configured to send configuration information of the control channelresource set to a terminal device, where the configuration informationof the control channel resource set includes indication information usedto indicate the position offset information.

The indication information used to indicate the position offsetinformation includes indication information used to indicate a physicalresource block number of the control channel resource set.

For example, the network device further includes a transmitter 702,configured to send a master information block MIB, where the MIBincludes indication information used to indicate an eleventh relativeposition of the control channel resource set relative to a referencepoint of a broadcast channel carrying the MIB.

For example, the configuration information of the control channelresource set includes at least one of a random access response RAR andradio resource control RRC signaling, and the control channel resourceset includes a type-1 common search space CSS and/or a terminal specificsearch space USS.

It may be understood that FIG. 23 shows only a simplified design of thenetwork device. In an actual application, the network device may includeany quantity of transmitters, receivers, processors, controllers,memories, communications units, and the like, and all network devicesthat can implement this application shall fall within the protectionscope of this application.

It should be especially noted that, for beneficial effects of thisembodiment, reference may be made to the method embodiment shown in FIG.2. Details are not described again herein.

An embodiment of this application further provides a terminal device,including:

a processor 801, configured to control actions of the terminal device,and perform processing performed by the terminal device in theembodiment shown in FIG.18, for example, configured to obtain an initialvalue for generating a first sequence or length information of a firstsequence, generate the first sequence based on the initial value or thelength information of the first sequence, and demodulate, by using thefirst sequence, a control channel signal carried in a control channelresource set, to obtain downlink control information.

For example, as shown in FIG. 24, the terminal device further includes areceiver 802, configured to receive a MIB, where the MIB includesindication information used to indicate a time-frequency resourceoccupied by the control channel resource set; and the processor isspecifically configured to determine a length of the first sequenceaccording to the indication information used to indicate thetime-frequency resource occupied by the control channel resource set.

For example, the processor is specifically configured to obtain one ormore of a synchronization signal, a broadcast channel scramblingsequence, a reference signal, or broadcast information that includes theinitial value for generating the first sequence.

For example, the terminal device may further include a memory 803,configured to store program code and data of the terminal device.

For example, the terminal device may further include a transmitter 804and a modem processor 805. The transmitter 804 is configured to adjust(for example, perform analog conversion, filtering, amplification, andup-conversion) an output sample and generate an uplink signal, where theuplink signal is transmitted to the network device in the foregoingembodiment by using an antenna. On a downlink, the antenna receives adownlink signal transmitted by the network device in the foregoingembodiment. The receiver 802 adjusts (for example, performs filtering,amplification, down-conversion, and digitization) the signal receivedfrom the antenna and provides an input sample. In the modem processor805, an encoder receives service data and a signaling message to be senton an uplink, and performs processing (for example, formatting,encoding, and interleaving) on the service data and signaling message. Amodulator further processes (for example, performs symbol mapping andmodulation) the encoded service data and signaling message and providesan output sample. A demodulator processes (for example, demodulates) theinput sample and provides a symbol estimation. A decoder processes (forexample, de-interleaves and decodes) the symbol estimation and providesdata and a signaling message that are decoded and sent to the terminaldevice. The encoder, the modulator, the demodulator, and the decoder maybe implemented by a composite modem processor 805. The units performprocessing based on a radio access technology (for example, an accesstechnology of LTE system or another evolved systems) used by a radioaccess network.

It should be especially noted that, for beneficial effects of thisembodiment, reference may be made to the method embodiment shown in FIG.18. Details are not described again herein.

An embodiment of this application further provides a network device. Thenetwork device including:

a processor 901, configured to control actions of the network device,and perform processing performed by the network device in the embodimentshown in FIG. 17. For example, the processor is configured to obtain aninitial value for generating a first sequence or length information ofthe first sequence, generate the first sequence based on the initialvalue or the length information of the first sequence, and map the firstsequence to a resource element carrying a reference signal in a controlchannel resource set.

For example, as shown in FIG. 25, the network device further includes atransmitter 902, configured to send a MIB to a terminal device, wherethe MIB includes indication information used to indicate atime-frequency resource occupied by the control channel resource set.

For example, the apparatus further includes a transmitter, configured tosend one or more of a synchronization signal, a broadcast channelscrambling sequence, a broadcast channel reference signal, or broadcastinformation that includes the initial value for generating the firstsequence to the terminal device.

It may be understood that FIG. 25 shows only a simplified design of thenetwork device. In an actual application, the network device may includeany quantity of transmitters, receivers, processors, controllers,memories, communications units, and the like, and all network devicesthat can implement this application shall fail within the protectionscope of this application.

It should be especially noted that, for beneficial effects of thisembodiment, reference may be made to the method embodiment shown in FIG.17. Details are not described again herein.

FIG. 26 shows a network device used in the foregoing embodiment. Thenetwork device is configured to perform processing performed by thenetwork device in the embodiment shown in FIG. 19. The apparatusincludes a processor 1001 and a transmitter 1002.

The processor 1001 is configured to generate a broadcast channelreference signal, where the broadcast channel reference signal includesa subset of a broadcast channel reference signal sequence.

The transmitter 1002 is configured to send the broadcast channelreference signal generated by the processor to a terminal device, andsend a MIB to the terminal device, where the MIB includes indicationinformation used to indicate a tenth relative position of the controlchannel resource set relative to the broadcast channel, and the subsetof the broadcast channel reference signal sequence and the indicationinformation of the tenth relative position are used to indicate positionoffset information.

It may be understood that FIG. 26 shows only a simplified design of thenetwork device. In an actual application, the network device may includeany quantity of transmitters, receivers, processors, controllers,memories, communications units, and the like, and all network devicesthat can implement this application shall fall within the protectionscope of this application.

It should be especially noted that, for beneficial effects of thisembodiment, reference may be made to the method embodiment shown in FIG.19. Details are not described again herein.

FIG. 27 shows a terminal device used in the foregoing embodiment. Theterminal device is configured to perform processing performed by theterminal device in the embodiment shown in FIG. 19. The terminal deviceincludes a processor 1101 and a receiver 1102.

The processor 1101 is configured to generate a broadcast channelreference signal sequence.

The receiver 1102 is configured to: receive the broadcast channelreference signal sent by a network device, where the broadcast channelreference signal includes a subset of the broadcast channel referencesignal sequence; and receive a MIB sent by the network device, where theMIB includes indication information used to indicate a tenth relativeposition of the control channel resource set relative to the broadcastchannel.

The processing module is configured to obtain position offsetinformation based on a ninth relative position corresponding to thesubset of the broadcast channel reference signal sequence received bythe receiver 1102 and the tenth relative position indicated by theindication information of the tenth relative position, and demodulateand decode, by using the first sequence, a control channel carried inthe control channel resource set, to obtain control information.

For example, the terminal device may further include a memory 1103,configured to store program code and data of the terminal device.

For example, the terminal device may further include a transmitter 1104and a modem processor 1105. The transmitter 1104 is configured to adjust(for example, perform analog conversion, filtering, amplification, andup-conversion) an output sample and generate an uplink signal, where theuplink signal is transmitted to the network device in the foregoingembodiment by using an antenna. On a downlink, the antenna receives adownlink signal transmitted by the network device in the foregoingembodiment. The receiver 1102 adjusts (for example, performs filtering,amplification, down-conversion, and digitization) the signal receivedfrom the antenna and provides an input sample. In the modem processor1105, an encoder receives service data and a signaling message to besent on an uplink, and performs processing (for example, formatting,encoding, and interleaving) on the service data and signaling message. Amodulator further processes (for example, performs symbol mapping andmodulation) the encoded service data and signaling message and providesan output sample. A demodulator processes (for example, demodulates) theinput sample and provides a symbol estimation. A decoder processes (forexample, de-interleaves and decodes) the symbol estimation and providesdata and a signaling message that are decoded and sent to the terminaldevice. The encoder, the modulator, the demodulator, and the decoder maybe implemented by a composite modem processor 1105. The units performprocessing based on a radio access technology (for example, an accesstechnology of LTE system and another evolved systems) used by a radioaccess network.

It should be especially noted that, for beneficial effects of thisembodiment, reference may be made to the method embodiment shown in FIG.19. Details are not described again herein.

An embodiment of this application provides a communications apparatus,including: a memory, configured to store computer executable programcode; a communications interface; and a processor. The processor iscoupled with the memory and the communications interface. The programcode stored in the memory includes an instruction, and when theprocessor executes the instruction, the communications apparatus has afunction for performing actions of the terminal device in the methodembodiment in shown in FIG. 2.

An embodiment of this application provides a communications apparatus,including: a memory, configured to store computer executable programcode; a communications interface; and a processor. The processor iscoupled with the memory and the communications interface. The programcode stored in the memory includes an instruction, and when theprocessor executes the instruction, the communications apparatus has afunction for performing actions of the network device in the methodembodiment in shown in FIG. 2.

An embodiment of this application provides a communications apparatus,including: a memory, configured to store computer executable programcode; a communications interface; and a processor. The processor iscoupled with the memory and the communications interface. The programcode stored in the memory includes an instruction, and when theprocessor executes the instruction, the communications apparatus has afunction for performing actions of the network device in the methodembodiment in shown in FIG. 17.

An embodiment of this application provides a communications apparatus,including: a memory, configured to store computer executable programcode; a communications interface; and a processor. The processor iscoupled with the memory and the communications interface. The programcode stored in the memory includes an instruction, and when theprocessor executes the instruction, the communications apparatus has afunction for performing actions of the terminal device in the methodembodiment in shown in FIG. 18.

An embodiment of this application provides a communications apparatus,including: a memory, configured to store computer executable programcode; a communications interface; and a processor. The processor iscoupled with the memory and the communications interface. The programcode stored in the memory includes an instruction, and when theprocessor executes the instruction, the communications apparatus has afunction for performing actions of the terminal device in the methodembodiment in shown in FIG. 19.

An embodiment of this application provides a communications apparatus,including: a memory, configured to store computer executable programcode; a communications interface; and a processor. The processor iscoupled with the memory and the communications interface. The programcode stored in the memory includes an instruction, and when theprocessor executes the instruction, the communications apparatus has afunction for performing actions of the network device in the embodimentin FIG. 19.

An embodiment of this application provides a computer readable storagemedium, where the computer readable storage medium stores aninstruction, and when a computer runs the instruction, the computer hasa function for performing actions of the network device in the methodembodiment in shown in FIG. 2.

An embodiment of this application provides a computer readable storagemedium, where the computer readable storage medium stores aninstruction, and when a computer runs the instruction, the computer hasa function for performing actions of the terminal device in the methodembodiment in shown in FIG. 2.

An embodiment of this application provides a computer readable storagemedium, where the computer readable storage medium stores aninstruction, and when a computer runs the instruction, the computer hasa function for performing actions of the terminal device in the methodembodiment in shown in FIG. 18.

An embodiment of this application provides a computer readable storagemedium, where the computer readable storage medium stores aninstruction, and when a computer runs the instruction, the computer hasa function for performing actions of the network device in the methodembodiment in shown in FIG. 17.

An embodiment of this application provides a computer readable storagemedium, where the computer readable storage medium stores aninstruction, and when a computer runs the instruction, the computer hasa function for performing actions of the terminal device in the methodembodiment in shown in FIG. 19.

An embodiment of this application provides a computer readable storagemedium, where the computer readable storage medium stores aninstruction, and when a computer runs the instruction, the computer hasa function for performing actions of the network device in the methodembodiment in shown in FIG. 19.

The controller or processor configured to perform the functions of thenetwork device and the terminal device in this application may be acentral processing unit (CPU), a general purpose processor, a digitalsignal processor (DSP), an application-specific integrated circuit(ASIC), a field programmable gate array (FPGA) or another programmablelogic device, a transistor logic device, a hardware component, or anycombination thereof. The controller/processor may implement or executevarious example logical blocks, modules, and circuits described withreference to content disclosed in this application. Alternatively, theprocessor may be a combination of processors implementing a computingfunction, for example, a combination of one or more microprocessors, ora combination of the DSP and a microprocessor.

Method or algorithm steps described in combination with the contentdisclosed in this application may be implemented by hardware, or may beimplemented by a processor by executing a software instruction. Thesoftware instruction may be formed by a corresponding software module.The software module may be located in a RAM memory, a flash memory, aROM memory, an EPROM memory, an EEPROM memory, a register, a hard disk,a removable magnetic disk, a CD-ROM, or a storage medium of any otherform known in the art. For example, a storage medium is coupled to aprocessor, so that the processor can read information from the storagemedium or write information into the storage medium. Certainly, thestorage medium may be a component of the processor. The processor andthe storage medium may be located in the ASIC. In addition, the ASIC maybe located in a terminal device. Certainly, the processor and thestorage medium may exist in the terminal device as discrete components.

A person skilled in the art should be aware that in the foregoing one ormore examples, functions described in this application may beimplemented by hardware, software, firmware, or any combination thereof.When this application is implemented by software, the foregoingfunctions may be stored in a computer-readable medium or transmitted asone or more instructions or code in the computer-readable medium. Thecomputer-readable medium includes a computer storage medium and acommunications medium, where the communications medium includes anymedium that enables a computer program to be transmitted from one placeto another. The storage medium may be any available medium accessible toa general-purpose or dedicated computer.

The objectives, technical solutions, and beneficial effects of thisapplication are further described in detail in the foregoing specificembodiments. It should be understood that the foregoing descriptions aremerely specific embodiments of this application, but are not intended tolimit the protection scope of the present invention. Any modification,equivalent replacement, improvement, or the like made on a basis of thetechnical solutions of this application shall fall within the protectionscope of this application.

1. A communication method, comprising: receiving, by a terminal device,a master signal block (MIB) message, wherein the MIB message comprisesfirst information indicating a time-frequency resource of a controlchannel resource set, and the time-frequency resource of the controlchannel resource set corresponds to length information of a demodulationreference signal sequence; obtaining, by the terminal device, thedemodulation reference signal sequence based on an initial value of thedemodulation reference signal sequence and the length information of thedemodulation reference signal sequence; and demodulating, by theterminal device using the demodulation reference signal sequence, acontrol channel signal carried in a control channel resource set toobtain downlink control information.
 2. The method according to claim 1,wherein the MIB message comprises configuration information of areference signal resource in the control channel resource set.
 3. Themethod according to claim 2, wherein the method further comprises:obtaining, by the terminal device, the length information of thedemodulation reference signal sequence according to the firstinformation.
 4. The method according to claim 1, wherein the methodfurther comprises: receiving, by the terminal device, a second MIBmessage, wherein the second MIB message indicates the length informationof the demodulation reference signal sequence.
 5. The method accordingto claim 1, wherein the obtaining, by the terminal device, thedemodulation reference signal sequence comprising: obtaining, by theterminal device, the initial value of the demodulation reference signalsequence according to information obtained based on a synchronizationsignal.
 6. The method according to claim 1, wherein the MIB message doesnot include indication information for determining a frequency domainreference point.
 7. A communication method, comprising: sending, by anetwork device, a master signal block (MIB) message, wherein the MIBmessage comprises first information indicating a time-frequency resourceof a control channel resource set, and the time-frequency resource ofthe control channel resource set corresponds to length information of ademodulation reference signal sequence; obtaining, by the networkdevice, the demodulation reference signal sequence based on an initialvalue of the demodulation reference signal sequence and the lengthinformation of the demodulation reference signal sequence; and mapping,by the network device, the demodulation reference signal sequence to atleast one resource element in a control channel resource set, whereinthe at least one resource element is used for transmitting ademodulation reference signal corresponding to the demodulationreference signal sequence.
 8. The method according to claim 7, whereinthe MIB message comprises configuration information of a referencesignal resource in the control channel resource set.
 9. The methodaccording to claim 7, wherein the method further comprises: obtaining,the network device, the length information of the demodulation referencesignal sequence according to the first information.
 10. The methodaccording to claim 7, wherein the method further comprises: sending, bythe network device, a second MIB message, wherein the second MIB messageindicates the length information of the demodulation reference signalsequence.
 11. The method according to claim 7, wherein the obtaining, bythe network device, the demodulation reference signal sequencecomprising: obtaining, by the network device, the initial value of thedemodulation reference signal sequence according to information obtainedbased on a synchronization signal.
 12. The method according to claim 7,wherein the MIB message does not include indication information fordetermining a frequency domain reference point.
 13. A communicationapparatus, comprising: a receiver, the receiver configured to receive amaster signal block (MIB) message, wherein the MIB message comprisesfirst information indicating a time-frequency resource of a controlchannel resource set, and the time-frequency resource of the controlchannel resource set corresponds to length information of a demodulationreference signal sequence; at least one processor; and one or morememories coupled to the at least one processor and storing programminginstructions for execution by the at least one processor to: obtain thedemodulation reference signal sequence based on an initial value of thedemodulation reference signal sequence and the length information of thedemodulation reference signal sequence; and demodulate, using thedemodulation reference signal sequence, a control channel signal carriedin a control channel resource set to obtain downlink controlinformation.
 14. The apparatus according to claim 13, wherein the MIBmessage comprises configuration information of a reference signalresource in the control channel resource set.
 15. The apparatusaccording to claim 13, wherein the programming instructions are forexecution by the at least one processor to: obtain the lengthinformation of the demodulation reference signal sequence according tothe first information.
 16. The apparatus according to claim 13, whereinthe receiver is further configured to: receive a second MIB message,wherein the second MIB message indicates the length information of thedemodulation reference signal sequence.
 17. The apparatus according toclaim 13, wherein the programming instructions are for execution by theat least one processor to: obtain the initial value of the demodulationreference signal sequence according to information obtained based on asynchronization signal.
 18. A communication apparatus, comprising: atransmitter, the transmitter configured to send a master signal block(MIB) message, wherein the MIB message comprises first informationindicating a time-frequency resource of a control channel resource set,and the time-frequency resource of the control channel resource setcorresponds to length information of a demodulation reference signalsequence; at least one processor; and one or more memories coupled tothe at least one processor and storing programming instructions forexecution by the at least one processor to: obtain the demodulationreference signal sequence based on an initial value of the demodulationreference signal sequence and the length information of the demodulationreference signal sequence; and map the demodulation reference signalsequence to at least one resource element in a control channel resourceset, wherein the at least one resource element is used for transmittinga demodulation reference signal corresponding to the demodulationreference signal sequence.
 19. The apparatus according to claim 18,wherein the MIB message comprises configuration information of areference signal resource in the control channel resource set.
 20. Theapparatus according to claim 18, wherein the programming instructionsare for execution by the at least one processor to: obtain the lengthinformation of the demodulation reference signal sequence according tothe first information.
 21. The apparatus according to claim 18, whereinthe transmitter is further configured to: send a second MIB message,wherein the second MIB message indicates the length information of thedemodulation reference signal sequence.
 22. The apparatus according toclaim 18, wherein the programming instructions are for execution by theat least one processor to: obtain the initial value of the demodulationreference signal sequence according to one or more configurationinformation obtained based on a synchronization signal.